Brexit negotiations between the UK and EU could be re-opened if MPs reject the deal negotiated by Theresa May this evening, Germany’s foreign minister has said.

Heiko Maas told reporters at the European Parliament: “The agreement stands, as it is. I doubt very much that the agreement can be fundamentally reopened. If there were a better solution, it would already have been put forward.”

He expressed hope that the withdrawal agreement could still pass, but added: “If it goes wrong tonight, there could be further talks.”

EU leaders and top officials in Brussels have previously rejected any suggestion that discussions could be re-opened. Commission officials have stated since December that they do not forsee any further meetings between the UK and EU.

The intervention by Mr Maas is likely to give succor to Tory MPs who hope to box the EU into offering more concessions by rejecting the agreement.

Though the EU has been emphatic that it will not drop the controversial Northern Ireland backstop, further talks could see changes to the political declaration on the future relationship.

The prime minister is heading for a significant defeat this evening on her plan, with projections suggesting that the margin of victory for the opposition could hit a new historic record.

Ms May spoke to Angela Merkel over the telephone at the weekend, leading to unsubstantiated reports in the UK press that Germany might ride to the rescue of the beleagured UK.

But a German government spokesperson told reporters in Berlin on Tuesday: ”The Chancellor has made no assurances beyond what was discussed in the European Council in December and what is laid down in the letter by Jean-Claude Juncker and Donald Tusk.”

"Brexit betrayal" march in London Show all 43 1 /43 "Brexit betrayal" march in London "Brexit betrayal" march in London A protester holds an anti-BBC sign Angela Christofilou/The Independent "Brexit betrayal" march in London A pro-brexit demonstrator holds a sign in the picket line Angela Christofilou/The Independent "Brexit betrayal" march in London A protester carrying a noose at the "Brexit betrayal" march. The man carrying it told a reporter: "That's what the traitor May deserves." 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in reference to the annual World Economic Forum meeting in Davos Angela Christofilou/The Independent "Brexit betrayal" march in London A protester holds a pro-brexit sign on the march Angela Christofilou/The Independent "Brexit betrayal" march in London The march approaches parliament Angela Christofilou/The Independent "Brexit betrayal" march in London A protester distributes pro-brexit lapel badges Angela Christofilou/The Independent "Brexit betrayal" march in London A demonstrator wears an anti-EU poster and holds an anti-BBC sign Angela Christofilou/The Independent "Brexit betrayal" march in London A smoke bomb is deployed in Parliament Square as the march comes across the counter-demonstration Angela Christofilou/The Independent "Brexit betrayal" march in London Angela Christofilou/The Independent "Brexit betrayal" march in London A flag bearing the Arms of Plantagenet flies in theprot Angela Christofilou/The Independent "Brexit betrayal" march in London Protesters on the Brexit 'betrayal' march in London on 9 December 2018 Angela Christofilou/ The Independent "Brexit betrayal" march in London Protesters on the Brexit 'betrayal' march in London on 9 December 2018 Angela Christofilou/ The Independent "Brexit betrayal" march in London Brexit 'betrayal' marchers gathering on Park Lane ahead of a protest on 9 December 2018 Angela Christofilou/ The Independent "Brexit betrayal" march in London Brexit 'betrayal' marchers gathering on Park Lane ahead of a protest on 9 December 2018 Angela Christofilou/ The Independent "Brexit betrayal" march in London Angela Christofilou/The Independent

The spokesperson added that an account of the phone call reported by The Sun newspaper and apparently sourced from UK government officials had been “incorrectly reproduced”.

The EU on Monday released a letter to the prime minister aimed at reassuring her MPs to vote for the deal, without changing its content. The bloc says it wants to conclude a trade agreement by 2020 and that its reassurances have "legal value".