THE UK Government has been accused of making a “significant retreat” from a key Brexit promise after Theresa May appeared to concede that a trade deal with the EU could not be signed until after the UK left the bloc.

Speaking during a visit to Jordan, the Prime Minister said she expected the shape of a new trade relationship to be clear to everybody by Brexit Day in March 2019 but appeared to accept that the formal conclusion of the agreement would have to wait until after withdrawal.

Last week, Donald Tusk, President of the European Council of leaders, left no doubt in his draft guidelines for negotiations that EU rules stated that trade deals could only be done with non-members; this meant that the most the UK could hope for prior to Brexit was an "overall understanding on the framework for the future relationship".

Any trade agreement would require unanimity among the EU leaders, a majority in the European Parliament, and ratification in all 27 national parliaments as well as in some regional parliaments, including that of Wallonia, which almost scuppered the deal with Canada. This means there are 36 legislatures, each with the power of veto.

Mrs May insisted it would be possible to reach clarity on the trade deal within two years but when asked if it could be finalised in that timescale, she said: "There's obviously a legal situation in terms of how the EU can conduct trade negotiations.”

She went on to say that she was clear that “by the point at which we leave the EU,” it would be right that everyone should know what the “future arrangements, the future relationship, that future partnership between us and the European Union will be”.

The PM added: "That's the sensible thing, it's the pragmatic way to look at this, and that's what we will do."

But her opponents, including pro-EU campaigners, seized on her comments.

Labour claimed Mrs May's comments amounted to a "significant retreat" from the Government's previous position that a trade deal could be done within the two-year deadline for withdrawal negotiations.

"It is less than a week since the Prime Minister triggered Article 50 and it seems every day brings another broken promise from the Government,” declared Paul Blomfield, the party’s Brexit spokesman.

"First they said immigration may go up after Brexit; now they are backpedalling on trade deals.”

The Sheffield MP accused UK ministers of trying to play down expectations.

His Labour colleague, Owen Smith, said: "Bit by bit, the main planks of the Prime Minister's Brexit strategy are falling away. Today, she has admitted that we will not have the time to agree a trade deal with the EU before the Article 50 period is finished."

Leaving without a trade deal would mean "our economy will go off a cliff edge, hitting our businesses with punishing tariffs and putting jobs at risk", said Mr Smith.

Meantime, Manfred Weber, the leader of the centre-right European people’s party and a close ally of German Chancellor Angela Merkel, warned a sector of the City of London would have to relocate to the continent post-Brexit, threatening an estimated 100,000 UK jobs.

At a press conference in Strasbourg, he said: “EU citizens decide on their own money. When the UK is leaving the European Union it is not thinkable that at the end the whole euro business is managed in London. This is an external place, this is not an EU place any more. The euro business should be managed on EU soil.”

John McDonnell for Labour said: “This threat to 100,000 jobs was all too predictable given the Tories’ extreme approach to the Brexit negotiations.”

Elsewhere, Sigmar Gabriel, the German Foreign Minister, following talks with Boris Johnson, the Foreign Secretary, in London warned the burden of not securing a deal was “higher” for the UK than the EU.

While he said Germany wanted to see a deal which held Britain "as close as possible" to the EU, Mr Gabriel stressed: “No-one should be left with the impression that the advantages of membership of the European Union can be used by people who are not members of the European Union."

Mr Johnson insisted it was possible to do a deal that was “win-win”.

He said: “I don't want to be unduly pessimistic; we can get a deal. But if you ask me: 'If we don't get a deal would the UK survive?' We would more than survive."