(CNN) UK Prime Minister Theresa May has announced yet another attempt to get her serially rejected Brexit plan through Parliament -- and this time she dangled the prospect of a second referendum to get it across the line.

May used a speech in London to outline what she claimed was a "new Brexit deal," which in reality looked a lot like her old Brexit deal with some added sweeteners designed to attract the support of dubious Members of Parliament.

"If MPs vote against ... this bill, they are voting to stop Brexit," May said.

In an attempt to repackage the plan, which has already been rejected three times by the House of Commons, May rolled it up into a wider set of legislation dealing with Britain's departure from the European Union. As well as the offer of a second referendum, it also contained pledges on workers' rights, environmental provisions, as well as a temporary customs relationship with the European Union.

Failure to agree the deal would lead to a "nightmare future of permanently polarized politics," she said.

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