British bookmaker William Hill suspended betting on the year that Prime Minister Theresa May will leave office, it said on Friday, amid speculation that she will face a confidence vote as she defended her draft Brexit deal.

"After the press conference on Thursday night, we thought Theresa had probably saved her job, but that is perhaps no longer the case," William Hill spokesman Rupert Adams said in a statement.

The move follows a report that May will face a no-confidence vote next week with Conservative lawmakers expected on Friday to submit the 48 letters required to trigger a leadership contest.

"It's almost impossible for us to predict what's going to happen," Adams told Reuters by phone, explaining that due to the uncertainty, the bookmaker was not able to price the different outcomes.

"We could be offering completely wrong prices," he said.

Former foreign minister and the figurehead of Britain's Brexit campaign Boris Johnson and Dominic Raab, who quit as Brexit minister on Thursday, are the bookmaker's favourite to replace May, William Hill said.

But gambling odds aggregator Oddschecker had Labour leader Jeremy Corbyn as favourite to fill May's shoes with odds of 5/1 on Friday, with Johnson and Home Secretary Sajid Javid joint second with odds of 8/1.

That would suggest punters expect succession will happen through a general election rather than just a Conservative Party mutiny.