The joke, by now, is wearing thin, but Sen. Joseph R. Biden Jr. (D-Del.) went along with it again yesterday as he was questioned by a pack of British journalists.

They wanted to hear him talk about plagiarism, the infamous deed that made him a headline figure in Britain and helped bring about the downfall of his campaign for the 1988 Democratic presidential nomination.

And so, on the occasion of British Labor Party leader Neil Kinnock's visit to the Senate as part of a two-day trip to Washington, a beaming Biden dutifully obliged.

"If and when he {Kinnock} becomes prime minister I hope he is still willing to recognize who I am and call me Joe, and occasionally use some of my material," Biden told the crowd of reporters and camera crews who broke into gales of laughter.

The joke was a reference to the controversy in 1987 when Biden, speaking in Iowa as he campaigned for the nomination, borrowed the Labor leader's words from a widely discussed Kinnock commercial from the previous summer's British general election.

Biden later acknowledged failing to credit Kinnock in the Iowa speech, which he called an oversight, and insisted that he had fully credited the Briton for the borrowed phrases in other campaign appearances.

Biden and Kinnock first met in London in 1988, when they were questioned extensively about the plagiarism incident. Yesterday was their second meeting, but the questions were the same.

"How are you two getting along?" they were asked.

"Well I have given him {Kinnock} a couple of copies of my speeches and I hope he uses some of them," Biden replied.

"This is going to be a thorn in Joe's side for a long time," one senior official said with a sigh. "He will never be able to meet Kinnock again without having the whole plagiarism episode replayed."

Kinnock laughed along, but his smiles were not altogether for the comments of Biden.

He was clearly pleased with his reception during this visit, which was in stark contrast to the cool welcome he received three years ago from Reagan administration officials because of his views supporting unilateral nuclear disarmament.

Senators from both sides of the aisle spoke of how "impressed" they were with the leader of the British opposition party and agreed that they could work with him if he became prime minister.

Sen. Richard G. Lugar (R-Ind.) said that if Kinnock became prime minister "he would have many friends here" in Washington.

Sen. Edward M. Kennedy (D-Mass.) spoke of Kinnock's "keen insights" into the changes taking place in both the Western and Eastern worlds. He said the Briton had been better received during this visit than in 1987 because there was a "better understanding of him."

Sen. Paul Simon (D-Ill.) added: "He is sensitive to our situation and he is sensitive to the global situation. I think it is in the minds of each of us that he will be the next prime minister of the U.K."