NEW YORK (AP) _ The regional director of the Federal Emergency Management Agency resigned Monday rather than alter a report that said disaster plans at the Shoreham nuclear power plant were inadequate.

Frank Petrone, who has been regional director for four years, charged that the Nuclear Regulatory Commission and Reagan administration officials had pressured FEMA to drop his criticism for fear it would interfere with Shoreham's licensing.

''What's taken place is not right,'' Petrone said at a news conference, calling the Shoreham licensing process ''a sham'' that will endanger the public.

''We're protecting lives here. I think that's our first and foremost responsibility,'' said Petrone, 40. ''And I really feel that we've neglected that.''

At issue is FEMA's report on its Feb. 13 test of the Long Island Lighting Co.'s plans to evacuate the area around Shoreham, 55 miles east of Manhattan, in an emergency. State and local governments have refused to participate, saying the plan could not work.

Petrone said he placed a statement in the report saying it was impossible for FEMA to assure that the Shoreham plant could be operated safely without state and local participation in emergency planning.

FEMA's director, Julius W. Becton, told him to remove the statement, quit, or be fired, Petrone said.

In Washington, FEMA spokesman Bill McAda said the dispute arose because Petrone insisted on making ''a finding as to the adequacy of the Shoreham plant,'' something it was not FEMA's role to do.

''I do fault the NRC,'' Petrone said. ''The NRC is continuing to go ahead. Be it the bureacrats, be it the composition of the commission, they're dead wrong. They should have stopped this sham before it got to where it is today.''

NRC spokeswoman Sue Gagnon said commission officials would have no comment because they had not reviewed Petrone's statement.

Gov. Mario Cuomo said in a statement that Petrone's charges should be investigated by Congress.

LILCO, Shoreham's builder, called Petrone's resignation an internal FEMA matter, and said the utility had no comment. It added: ''Whether or not the emergency plan can be implemented is before the NRC for determination.''