LONDON — Weakened by the loss of her parliamentary majority, Britain’s prime minister, Theresa May, pressed ahead on Thursday with legislative plans to extract her country from the European Union, publishing a dense, technical bill that will ultimately test her fragile grip on the job she wrested from a pack of rivals a year ago.



After her gamble in calling an early general election backfired last month, Mrs. May now faces the formidable task of negotiating with the other 27 European Union member countries while knowing that she could be undercut by her own Parliament at any time as she pushes ahead on British withdrawal, known as Brexit.

Amid open speculation about her political longevity, Mrs. May had little to celebrate on her anniversary in Downing Street, and on Thursday she told the BBC that she had shed a “little tear” when she first learned of exit polls indicating that her decision to hold a general election had deprived her Conservative Party of its majority.

Her mood may not have been lifted by colorful criticism from Amyas Morse, the head of the National Audit Office, a respected spending watchdog. He compared the government’s approach to Brexit to a chocolate orange, a treat popular in Britain, in that it might fall apart “at the first tap.”