The great veil of secrecy enveloping the prime minister's influential Cabinet committees has been pierced for the first time here by the weekly New Statesman.

A detailed analysis by editor Bruce Page concludes that the system makes the Prime Minister much more than a first among equals and is turning Britain's cabinet style of government into something like a presidential system.

Ever since the start of this century, when government here took on more responsibilities and the Cabinet was split into committees to deal with them, enormous secrecy has surrounded the technique. Both the subject matter and the membership of these committees has been held secret. Some governments have even denied they exist.

Indeed, a parliamentary select committee once discovered that Cabinet committees, like telephone tapping or security arrangements at Chequers, the prime minister's country residence, are subjects which successive prime ministers have refused to discuss in the House of Commons.

In the United States, Congress, academics, journalists and an interested public would soon pry loose any internal organization of the White House that a president attempted to keep secret. Here, however, there is surprisingly little interest in the subject and page's enterprise has gone largely unnoticed except in The Times.

There is still an old fashioned belief here that the Cabinet deliberates on policy and Parliament then debates and decides it. There is little understanding of what Walter Bagehot, the great commentator, discovered a century ago, that the Cabinet is an "efficient" part of government and Parliament, like the monarchy, was becoming a "dignified" part.

In fact, Bagehot needs amending in the current climate of minority governments. Parliament is enjoying a revival of at least nay-saying power in this new era.

But the crucial fact remains that policy can be shaped only within a Cabinet.Moreover, within that Cabinet, he who controls the membership of its tropical committees controls the essence of policy and that person is the prime minister.

Following Page's article, there very likely will be more awareness of the Cabinet committee function. Nevertheless, while a member of Prime Minister James Callaghan's staff confirms much of what Page has written, he still defends the secrecy rule.

This official argues that secrecy spares ministers on special interest committees from lobbying and preserves the British notion of collective Cabinet decisions are heavily influenced by the committees but contends that in the end their recommendations must be approved by the Cabinet as a whole. He agrees with Page that the technique does enhance prime ministerial power, but notes the right to appoint and fire ministers does the same.

Two examples in the New Statesman article undermine at least some of the secrecy defense. One case involves Britain's forthcoming fourth television channel. The BBC now has two, commercial independent television has one and both strongly oppose any new, third body getting the next.

According to Page, top civil servants and the Home Office, which supervises television, all support the broadcasters' view. Sir John Hunt, secretary to the Cabinet, and a key civil servant, proposed a Cabinet committee that was likely to produce a broadcasters' recommendation.

But Callaghan, unenthusiastic about the way the two broadcasting hierarchies treat politicians, favors a new, open broadcasting authority for the fourth channel.

So, according to the account, he made himself chairman of the Cabinet committee and stacked it with three other like-minded ministers - Tony Benn, Roy Hattersley and William Rodgers. They and their colleagues, Page said, were heavily lobbied by both the BBC and independent television, an indication that secrecy does not stop important interests here from finding out who serves.

In the next few days, the government is expected to issue a white paper reflecting the views of Callaghan and his majority on the committee. Thus the prospects of a new broadcasting authority here have been increased greatly.

In much the same way, Page discloses, Callaghan stacked a committee that produced a white paper last week burying any hopes for a freedom of information act. Instead, the proposed "reform" of the Official Secrets Act would simply make it a more useful instrument to suppress leaks, according to most of the press.

Again, this is what Callaghan himself has publicly urged and he chaired the relevant committee. This time he reportedly left off Hattersley and Benn, two ministers from the right and left with a passionate interest in more open government.

In all, Page estimates there are about 20 to 25 permanent or standing committees, of which half are consequential. In addition, Callaghan has named about 130 ad hoc committees to deal with temporary issues.

On the world scene, the most important is DOP, dealing with defense and foreign policy. Besides the foreign secretary, home secretary and chancellor of the Exchequer, the chief of the defense staff normally attends its meetings, Page writes. This makes him unique in government and gives him extra clout with which to plead the armed services' case for more cash.

At home, the "first team" sits on EY or economic strategy. The use of the symbol "Y" may reflect the economists' shorthand for income.

Callaghan chairs this committee and it includes Denis Healey, chancellor of the exchequer, Meryln Rees, home secretary; David Owen, foreign secretary; Michael Foot, leader of the Commons; Eric Varley, industry; Benn, energy; Hattersley, prices; Albert Booth, employment; Peter Shore, environment; Edmund Dell, trade; Shirley Williams, education; Harold Lever, the Cabinet's economic adviser, and Joe Barnett, chief secretary to the treasury.