WASHINGTON (AP) _ Immigration Commissioner Gene McNary said Thursday he was studying a plan to bar Central Americans from working in overloaded labor markets such as Miami and San Diego while seeking political asylum.

Under the plan being reviewed by the Immigration and Naturalization Service, work permits issued to aliens applying for political asylum would restrict them from taking jobs in cities where there is a glut of cheap labor caused by a large concentration of new arrivals.

The work permits ''may exclude Miami or San Diego or areas that are overrun at the present time'' by aliens, McNary said.

In Miami alone there are 50,000 people, mostly Central Americans, seeking refugee status. The large concentration of would-be refugees places a strain on the local labor market and on community social services.

McNary said he has asked the INS general counsel to review whether the agency has legal authority to place such restrictions on work permits granted to people who are applying for political asylum.

Arthur Helton, director of the Lawyers Committee for Human Rights' refugee project, said restricting work permits would be an unlawful travel restriction under the Constitution and the United Nations refugee protocol.

Helton said ''the only humane solution'' is to spend more money to hire more INS examiners to speed up the processing. Delays of months and years only encourages people to apply for work permits, he said.

The new immigration commissioner, who took office Oct. 26, acknowledged in an interview with reporters that, ''I don't feel as though I have control'' of the sprawling agency that has been criticized for mismanagement.

Some decisions have been made without approval of headquarters but ''will be brought under our management,'' McNary said.

Under McNary's predecessor, Alan Nelson, INS came under repeated criticism for mismanagement and inefficiency. An audit ordered by Attorney General Dick Thornburgh sharply criticized the management of the agency under Nelson.

While being careful not to criticize Nelson, McNary said: ''I am aware of a number of audits that have been conducted and are ongoing. I view that as a benefit.''

The commissioner said he has taken steps to centralize the agency's budget, procurement, hiring and policy development.

The lines of authority must be clarified because ''we have people who are taking orders from two different sources,'' McNary said.

Because of the diversity of statements by INS officials around the country, McNary said he had ''found myself at a loss as to what the policy was'' on certain issues.

''There is going to be one policy and it's going to be established here at the central office,'' said McNary, who last month ordered INS officials to clear public statements with Washington.

The new commissioner said he wants to streamline deportation proceedings, which often take years to complete because of cumbersome administrative appeals.

''The way INS handles deportation is absurd,'' he said. ''Any lawyer can kick a case for years.''

McNary said he needed more time to determine whether INS would continue to deport Nicaraguans who came to this country.

About 70 were deported last spring after a crackdown on the Texas-Mexico border. During an eight-month period, as many as 60,000 Central Americans entered this country.

Nicaraguans have enjoyed a special status in the sense that any INS deportation order is reviewed by a special Justice Department unit set up during the Reagan administration.

McNary also said he plans to issue new regulations for determining if an alien has a well-founded fear of persecution and is therefore eligible for political asylum.

''Our adjudicators don't have the training they should have, as a result there may be mistakes made,'' McNary said.

McNary said he had no plans to change the INS policy of interviewing Haitians on Coast Guard cutters that intercept boat loads of people headed toward U.S. shores.

McNary said he would not consider conducting the processing of these Haitians on U.S. soil because that would mean ''crossing the line of exclusion to deportation and deportation is a major problem.''

The Coast Guard intercepts one or two boatloads of Haitians a month on the high seas. Those refused political asylum by INS inspectors are turned back to their native land, a practice that has been criticized by groups favoring a more open immigration policy for Haitians.