Dan Norris, a lawmaker who won a seat in Parliament last year, was swiftly suspended from Britain’s governing party.

Mr. Morris “was immediately suspended by the Labour Party upon being informed of his arrest,” the party said in a statement, adding that it “cannot comment further while the police investigation is ongoing.”

The party did not specify why Mr. Norris, 65, had been arrested, and he did not immediately respond to a request for comment on Saturday.