Meeting in Parliament, lawmakers were unanimous in saying Mr. Trump, by giving a platform to the fringe group Britain First, had gone too far.
The chorus began after Stephen Doughty, a Labour lawmaker from Wales and the grandson of an American G.I. who came to Britain in 1944 to fight Germany, used a parliamentary maneuver to call an urgent debate on “Britain First, online hate speech and the sharing of inflammatory content online by the president of the United States, Donald Trump.”
The government minister present, Amber Rudd, the home secretary, made no attempt to defend Mr. Trump, though she observed that sharing intelligence with the Americans “has undoubtedly saved British lives.”
Members of the opposition Labour Party had been among the first to pounce on Mr. Trump’s tweets, but they were joined on Thursday by several members of Mrs. May’s Conservative Party.
One of them, Peter Bone, called on Mrs. May to persuade Mr. Trump to delete his Twitter account. Another, Tim Loughton, urged Twitter to take down Mr. Trump’s account “as it would that of any other citizen of the world who peddled such hate.”
A third Conservative lawmaker, Paul Masterton, lamented: “Just because somebody stops using Twitter, it does not mean that they cease to be a twit.”
Remarkably, a Parliament that in February debated whether to deny Mr. Trump a state visit because, among other reasons, it could embarrass Queen Elizabeth II, found itself taking on that question once again.
For Mrs. May, the episode has been simultaneously an embarrassment, a diplomatic setback and a lesson in just how hard it is to manage her relationship with Mr. Trump, a leader she has tried hard to cultivate.
Britons pride themselves on their “special relationship” with the United States and, this week, basked in the announcement of the engagement of Prince Harry to the American Meghan Markle.
But by the middle of the week Mr. Trump had knocked news of the royal wedding off the front pages, replacing it with a renewed discussion of whether a state visit to Britain should be scrapped.
Mr. Khan — the London mayor who was involved in a separate dispute with Mr. Trump after a terrorist attack in his city —…