Leaders of America's largest railroad union yesterday urged Congress to study possible nationalization of their industry, in a bitter response to rail management proposals that freight train crew sizes should be reduced.

United Transportaiton Union president Al H. Chesser characterized the decision by most railroads, to seek an overhaul of work rules in negotiations for new union contracts, as evidence "regressive and unenlightened . . . management, that only a few years ago guided this industry to the very brink of self-destruction, is apparently once again in control."

Chesser told reporters at a news conference here that the railroads' action amounted to a "big double cross," included the "most inept, antiquated, asinine" demands he ever had seen represented "stupid management practices" and added up to "inciting our people to strike even before negotiations get under way.

The union leader also asserted that the railroads were acting illegally in seeking to negotiate the size of freight train crews on a national basis. He said such bargaining may be conducted only on a company-by-company basis, citing a 1967 court decision on the issue which found that national bargaining on crews was not required.

Chesser said flatly that the UTU would not bargain on the crew issue in the current national talks, raising the possibility of an early impasse between labor and management which could be followed by court action or federal government intervention.

A spokesman for the rail industry, Dan Lang of the National Railway Labor Conference, said he did not know what will happen next" but that railroad officers believe proposals sent to the union "are legal."

So angry was Chesser that he twice knocked down a microphone while delivering his verbal assualt on the industry, less than 24 hours after initial bargaining for new contracts began in Chicago. Negotiations between 21 unions and 58 rail firms are scheduled to resume here next Monday on contracts to replace those that expire at the end of 1977.

Chesser's news conference was the first significant public response by labor to the industry's bargaining proposals, sent last month by the National Railway Labor Conference to the UTU, representing 185,000 brakemen, conductors and engineers, and the 37,000-member Brotherhood of Locomotive Engineers.

With the significant exception of Consolidated Rail Corp., the largest U.S. railroad in terms of freight business and employees, most railroads are represented by the rail labor conference in the current talks.

Focusing on three key areas, the industry proposed elimination of work rules that require four crew members on most trains (engineer, conductor, two brakemen); an end to 19th Century rules establishing 100 miles of travel or eight hours of work as being a full day; and company flexibility in assigning some train crews to do yard work.

William H. Dempsey, current president of the Association of American Railroads and previously head of the industry's rail labor conference, told a recent rail conference the work rules at issue are "mired in the last century." Elimination of the rules could save rail rirms $1 billion a year in payroll costs, he estimated.

Consolidated Rail (Conrail) is not bargaining with other railroads for new contracts because of separate labor discussions started soon after the 15-month old firm was set up as a federally aided successor to the bankrupt Penn Central and other Northeast and Midwest lines.

Chesser pointedly singled out Conrail for praise yesterday, stating it now has the "best management" in the rail industry and has created "one of the best railroads." Conrail "is not in this movement (to change work rules, (they have more sense," Chesser added.

in addition to Conrail, other railroads that have declined to join the industry in seeking work rule changes are the Chicago, Rock Island & Pacific (also has withdrawn from all other negotiations), the Chicago & North Western, Boston & Maine and Bangor & Aroostock.

Chesser said that after the 1967 court ruling his union negotiated more than 100 contracts with various railroads on reduced crews for specific trains but he told reporters than in the past two years, less than a half-dozen proposals on reduced crews have been sent to the union by individual railroads.

If the crew issue is removed from national bargaining proposals, the UTU is "ready to sit down and talk on any individual property . . . we'll talk to any carrier," Chesser stated.

The union chief said that while he has "always been opposed to nationalization of any industry," the request to Congress for "an indepth study" is necessary because "this country can no longer stand the folly of rail management irresponsibility to the country."

In response to questions, Chesser said the proposed study has been discussed with members of Congress he declined to identify. It should take about six months to complete and if it concludes that nationalization is the proper course. "Yes, I'd support it." Chesser added.

The UTU president also vowed to issue a new set of proposals on behalf of his members, now that management has "forced my hand." The railroads soon will get some proposals for "real deserving working conditions," he said.

Already, the UTU and other unions have proposed three annual pay increases of 15 per cent each plus other benefits that industry officials said could mean a three-year package amounting a 75 per cent increase in wage costs, over the three years starting next Jan. 1.

According to Labor Department data, railway workers averaged $6.98 an hour in 1976. Other government statistics show average rail worker s earned $19,246 in 1975.

But Chesser cited rail industry data filed with the government showing that the number of rail executive officials increased between 1960 and 1975 by more than 13 per cent to 17,000 while the number of other employees declined 33 per cent to 477,000.

Pay for top exeutives and officials rose from $4.93 an hour to $11.32 over the same period while wages for other employees increased from $2.69 to $6.12 an hour. He also complained about high salaries being paid top rail company chairmen and said they should take pay cuts.