About once a month, a group of financiers meet in the headquarters of British Rail to discuss art. Actuaries and accountants debate Renoir and Picasso.

But these men who gather to consider old masters are more interested in investment than esthetics. Thye are the Art Subcommittee of the pension fund of the government-owned British Rail.

Over the past four years they have assembled one of the world's largest art collections, believed equal to that of the Rockfellers and valued at mroe than$50 million.

Since 1974 the pension fund has been seeking investment security through art purchases. A sharp recession that year, combined with an inflation rate approching 30 percent, made conventional investments appear to be a less-than-certain source of continued revenue to support the fund's one million pensioners.

But what may have seemed a good idea four years ago latelyhas been coming under increasing attack. Critics complain that the fund's purchasing is done in secrecy, that its acquisitions are kept out ofpublic view and that, as one member of parliament put it, a "slightly sinister" relationship exists between the Dund and Sotheby's, the auctionhouse, which acts as both adviser and purveyor to British rail.

This past year alone, the fund spent close to$15 million enlarging its collection in a policy described as "almost unique" in the investment world.

But, argued labor member of parliament Andrew Faulds, who has repeatedly criticized the British rail scheme, that "investment is as dangerous as attempting to beat card sharps at their own game."

Another M.P., Norman Fowler, disliked investing public funds in antiques and works of art because it was essentially speculative.

"The art market is subject not only to supply and demand, but to shifts in taste. No one claims that it is an investment to help industry or to produce jobs, and that is something that worries rail union leaders," Fowler said.

John Morgan, the manager of the pension fund's investment portfolio is presently given to art-and at most, only 5 percent would ever be invested. But that figure is nearly eight times larger than the acquisitions budget of the National Garlery and nearly 20 times greater than the British Museum's.

Morgan stated recently that "the nature of the art world shows that works of art are a way of beating inflation." In much of the critism, Morgan sees traces of snobbery-the implication that "railwaymen's pensions should have nothing to do with high art." Also, an unpsoken assumption exists that if money is to be lost, and Morgan does not believe that is happening, then "it should be lost more respectably."

One official of the fund, Christopher Lewin, has stated that "statistics show that over the past 25 years works of art-despite a lack of day-to-day income-actually produced a higher return than investments in ordinary shares."

At the same time, fears have been expressed several times recently by dealers and collectors that British Rail is paying extraordinarily high prices for pieces; hence, the market becomes artificially inflated and the profit on reselling becomes smaller.

"I think it is quite wrong that taxpayer's money should be used to buy precious things and to distort the market," asserted a Conservative parliamentarian.

In April the fund paid a record $175,000 for a Vincennes porcelain group at an cuction in Monte Carlo. Several London porcelain dealers stated at the time that price was "two or three times too much." Serious doubt exists as to when the porcelain was painted, a question on which the object's value heavily leans.

Two years ago, as well, the fund dropped $1 million on a Picasso watercolor that experts contend was worth $600,000 at most.

On the other hand, with the help of an unnamed intermediary, the fund secured a prize collection of old masters paintings from the estate of the Duc de Talleyrand last May for about $2 million. One museum expert, speaking of the fund's purchase, said it had done "extremely well."

Overseeing the entire acquisitions process is Anna Maria Edelstein. A native of Italy and a former Sotheby's employe, Edelstein admits that "yes, sometimes one buys at high prices. Sometimes, because it is a bad day or because other dealers weren't there, you buy low. Sometimes that next day I have been offered a very generous profit on something I have just bought."

Before Edelstein is allowed to bid on a piece, the Art Subcommittee reviews the proposal. "We accept only one out of three," said Morgan. The Art Subcommittee makes its decision in secret and, to the dismay of some critics, very rarely announces its purchases even after it makes them. But Morgan contends that this is vital to protect the fund against unscrupulous dealers.

Explains Lewin, "Specialized collections of art attract much more attention than those that are higgledy-pigledy, and consequently higher prices when sold." Secrecy thus becomes important-otherwise dealers would be able to recognize the specialist collections the fund was trying to build up.

"They would then know which items we would particularly need," he noted, "and the result would be that we would have to pay more for them."

The veil of secrecy is maintained even when objects from the collection are put on show. About 40 percent of the fund's 640 pieces are on exhibit around the United Kingdom. But many of them bear the label "Anonymous Loan." A significant chunk of the collection, though, surfaced recently in Doncaster, and old reilroad town in the north of England. Eleven 17th-century Dutch paintings, along with several other objects d'art , were put on long-term loan at the local museum, and only by accident did the name of the benefactor emerge.

In Edinburgh, a third-century B.C. bronze statue of Poseidon went on exhibit last month with an "Anonymous Loan" tag. Art dealers are generally convinced that the piece belongs to British Rail, but the pension fund is most reluctant to acknowledge it, because some question has arisen as to whether the statue was exported from Italy legally.

Other pieces known to be in the collection include a Renoir portrait of Cezanne dated 1880; a 1779 bust of Benjamin Franklin by Houdon, similart to he one in New York's Metropolitan Museum; a sketch for a ceiling fresco by Tiepolo; some unspecified Canalettos and a whole range of other items from Louis XVI ormolu candelabra to a German silver gilt coconut cup and cover.

Several of these pieces are presently on exhibit at the National Gallery and the Victory and Albert Museum.

"But what of the rest-consisting of some $40-million worth-that have been bought over the past few years?" critic Faulds asks.

In fact, the bulk of the collection sits in vaults. Morgan says that the fund would like to have more on show, but many museums are cramped for exhibition space as its is, with some of their own prize possessions being relegated to basements. Further, very few museums can meet the strict requirements for maintenance that the fund requires.

That high level of curatorship is left to a subsidiary of Sotheby's James Bourlet, who store, pack, ship and restore much of the pension fund collection. This arrangement is necessarily profitable to Sotheby's. That does not rankle critics so much as the fact that Sotheby's receives a fee from British Rail for the advice it provides, as well as a 10 percent commission on the enormous sums the pension fund spends at Sotheby' sales.

"If ever there were a conflict of interest," complained Faulds from the floor of the House of Commons, "that must rank as one of the worst examples."

"Auctioneers should act as agents only, and not principals," Faulds continued. "The danger is that as owners of the objects, Sotheby's must be tempted to ensure the best return."

The satirical magazine Private Eye points out in a sober article on the British Rail-Sotheby relationship that those objects placed in museums are revalued each year by museum staff at the urging of the pension fund-Sotheby team.

"This means that the collection becomes considerably over-valued because the price of most antiques and works of art does not rise that fast. Art valuations are a bit of a racket at the best of times."

Even Edelstein says: "You can take an object to five different dealers and get five different valuations."

But Private Eye goes on to assert that since a valuation is "endorsed by the Victoria and Albert's expers, it carries more authority than most. And the benefits of a prestigious over-valuation when the time comes from resale do not have to be over-emphasized."

The Victoria and Albert has reportedly become fed up of late that it is being forced to accept unwanted itesm from the pension fund at vastly inflated insurance values.

"What is good for Sotheby's," challenges M.P. Robert Adley, "may not necessarily be good for the British taxpayer."

Morgan admits that the relationship between the fund and Sotheby's "is open to misunderstanding," but argues that enough precautions have been taken to avoid a conflict of interest. He insists that there is a sufficient "air lock" between the two sides, and he argues that the pension fund needs advice and Sotheby's established expertise is vitally necessary.

"The Art Subcommittee are hardheaded businessmen," he continues. "We do not delegate managerial authority because we are working with art."

Sotheby's refused any comment, saying it does not discuss the affairs of its clients.

Faulds has called for an independent evaluation of the entire British Rail collection-and possibly a government order forbidding future purchases.

"British Rail," says Faulds, "states with sanctimonious soleminity, after a good deal of questioning, that the works of art which have been acquired ase nort still around-and the likelihood is that they will not be-will be able to make up a multitude of excuses as to why so many of their purchases have failed to live up to their expectations."

Such dire predictions have not stopped Edelstein. She travels about every other month to sales centers like New York, Zurich or Geneva with her go-carefully calculated price limits, along with extensive data on authenticiy, insurance, storage problems and so on.

I sometimes spend sleepless nights before sales wondering whether we have put the right price on something," she confesses.