Peter Jay, whose appointment as British ambassador to the United States last May, created a controversy itself, caused a new flap today by flying in an American-built Boeing 747 instead of the British Concorde to his new job.

Jay, the son-in-law of Prime Minister James Callaghan, chose the slower British Airways 747 because the flight to Washington was $162.65 cheaper than the Concorde, the Foreign Office said. "Also, time was not of the essence," a spokesman said.

The London Daily Mirror called Jay's snub "a kick in the fuselage" to the Concorde.

"The taxpayer has been milked already to build the Concorde," the Mirror said. "But if Britain's No. 1 man in America doesn't think it worth paying extra to fly Concorde, why should anybody else?"

"This is disgraceful but not surprising," Robert Adley, a pro-Concorde member of Parliament, said of Jay's action. "He has always been anti-Concorde."

The Concorde was also in the news in Paris is where about 50 Communist militants invaded a television studio and disrupted an evening news program with a demand that the newscaster read their manifesto favoring long-sought New York landing rights for the Concorde.

Viewers saw a few minutes of scuffling before the news went off the air and was replaced by a film of landscapes with soft music playing.