British Prime Minister Theresa May is warning lawmakers they could take Britain into "uncharted waters" and trigger a general election if they reject her Brexit deal in a crucial parliamentary vote this week.

May is fighting to save her unpopular Brexit plan and her job ahead of a showdown in Parliament planned for Tuesday, when lawmakers are widely expected to reject the Brexit divorce deal she struck with the European Union. Her Downing Street office insisted that the vote will go ahead amid speculation the government may be forced to delay it.

In an interview with the Mail on Sunday, May said rejecting her deal would "mean grave uncertainty for the nation with a very real risk of no Brexit or leaving the European Union with no deal."