A congressman who met with President Reagan yesterday said he implied that he would rehire some of the 15 executive branch inspectors general summarily fired on Wednesday.

Rep. Frank Horton (R-N.Y.), ranking minority member on the Government Operations Committee, which created the inspector general legislation, quoted Reagan and his senior staff as saying that their intent was not to politicize the office, but to keep those inspectors general doing the best jobs and replace the others.

On Wednesday the White House notified all the inspectors general of their firing, effecitve the day before. The announcement came without warning, even after some inspectors general received favorable recommendations from Reagan transition aides. Some of those dismissed heard of their firing Wednesday night on television.

Some of the sponsors of the Inspector General Act of 1978 expressed concern yesterday that Reagan was politicizing an office they intended to be filled with talented people without regard to political affiliation. The IGs, who operate independently of Cabinet secretaries, oversee the work of thousands of auditors and investigators who watch over the expenditure of federal funds.

Sen. Thomas F. Eagleton (D-Mo.) wrote Reagan that he feared "that an indiscriminate removal of all IGs . . . will inflict a real setback in the battle against fraud and waste."

Several IGs contacted yesterday said they were dismissed, but some said they would apply for reappointment. Horton said Reagan had told him that his intentions had been misunderstood, and that his staff would give careful consideration to those who wanted to remain on the job.