No confidence vote about to be triggered in UK PM May, Sky News reporter

Some lawmakers in Prime Minister Theresa May's Conservative Party are confident that enough letters of no-confidence have been submitted to trigger a leadership challenge, the deputy political editor of Sky News said on Tuesday.

"My ERG sources pretty confident now that 48 trigger been breached," Beth Rigby said on Twitter.

A leadership challenge is triggered if 48 Conservatives write such letters to the chairman of the party's so-called 1922 committee, Graham Brady. May could be toppled if 158 of her 315 lawmakers vote against her.

"Of course Sir Graham won't announce while PM out of the country - and we've been here before. But mood hardening," Rigby said.

The European Research Group (ERG) is a group of Eurosceptic British lawmakers.