(Bloomberg) -- The British Parliament will vote against the latest proposal for Brexit because it risks tying the U.K. into the bloc’s trade rules forever, Prime Minister Theresa May’s Cabinet was told on Tuesday.

According to people familiar with the matter, government Chief Whip Julian Smith told a Cabinet meeting the current plan for a so-called backstop guarantee to avoid a hard border with Ireland will not have enough votes to pass the House of Commons.

May has promised Parliament a “meaningful vote” on whether to approve or reject any final Brexit deal she reaches with EU. But hopes of reaching an agreement rest on resolving the current impasse over how to ensure there is no need for customs checks at the land frontier between Northern Ireland and the Irish Republic.

Cabinet ministers discussed the issue for two and a half hours on Tuesday, and agreed that the EU’s proposals aren’t good enough. The ministers said they wanted a guarantee that if the whole U.K. stays in the EU customs regime it will be a time-limited measure.

And they objected to the EU’s proposal for a final, fall-back option under which Northern Ireland will remain inside the bloc’s customs territory, while the rest of Britain leaves. May has said she can never accept that idea because it would put a customs border inside the U.K.

Smith made clear his calculations showed members of Parliament held similar reservations and would not consent to the EU’s proposals, if they were ever put to a vote, the people said.

To contact the reporter on this story: Tim Ross in London at tross54@bloomberg.net

To contact the editors responsible for this story: Flavia Krause-Jackson at fjackson@bloomberg.net, Emma Ross-Thomas

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