British Prime Minister Theresa May has passionately appealed to British MPs to support the Brexit deal in tomorrow's House of Commons vote.

The last-ditch attempt to convince them to endorse the deal follows the publication of a new letter from the EU to the British government.

The letter provides clarifications on the Irish backstop, saying it would only ever be temporary and there can be no renegotiation.

The DUP, which props up Mrs May's government, said the clarification had not swayed its intention to vote against the deal.

The DUP's Westminster leader Nigel Dodds said the letter from EU Council President Donald Tusk and EU Commission President Jean-Claude Juncker "changes nothing".

Earlier, Mrs May addressed workers at a factory in the English city of Stoke-on-Trent.

She insisted that if the referendum result is not honoured, people's faith in politics will suffer "catastrophic harm".

Mrs May now believes, Downing Street says, that "based on the evidence of the last week", MPs managing to block Brexit is more likely than the UK leaving the EU without a deal.

The UK is set to leave the bloc by default on March 29th.