Prime Minister Theresa May made a desperate final gamble to get her Brexit deal through the British Parliament before she's thrown out of office - but her efforts look doomed.

In a hastily arranged speech, the embattled May promised to give members of Parliament a vote on whether to call another referendum to ratify the terms of Britain's divorce from the European Union.

It's something many MPs - including scores in the opposition Labour Party - have been calling for, but she made it conditional on them backing her deal first.

Within minutes of her speech ending, the backlash began.

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Pro-Brexit Conservative MPs lined up with the Opposition Leader Jeremy Corbyn and May's Northern Irish allies to condemn her proposals. They vowed to vote against them in the House of Commons next month.

May's latest offer represents possibly the final throw of the dice for a Prime Minister who has run out of options.

Almost three years after the UK voted to exit the EU, May's deal has been rejected three times by Parliament. She's tried cross-party talks to work out a joint plan with Corbyn but they collapsed last week.

May has promised to put her deal, in the form of a draft law, to a vote in Parliament in the first week of June. Facing overwhelming calls for her to resign, the Prime Minister has promised to agree to the timetable for her own exit once that vote has taken place. Barring a political miracle, May is headed for a humiliating end to her career.

"I have tried everything I possibly can to find a way through," May told an audience in central London. "I offered to give up the job I love earlier than I would like."

The Prime Minister said that although the cross-party talks with Labour have failed, most MPs still want to deliver the result of the 2016 referendum. Then she set out her offer of "one last chance to do that."

As part of a 10-point plan, May promised:

- A choice for Parliament over the kind of customs model the UK should have with the EU after Brexit.

- A guaranteed vote on whether to call a second referendum to ratify the terms of the exit deal, before Parliament can approve the divorce.

- Alternative arrangements to mitigate the impact of the so-called "backstop" plan to for avoiding a hard border with Ireland.

But first members of the House of Commons will need to vote in favour of May's overall divorce deal in the first week of June.

- Bloomberg