THERESA May has come under sustained attack from senior figures within her own party over the direction of travel towards Brexit.

Former chancellor George Osborne yesterday warned Mrs May that leaving the single market risked being the "biggest act of protectionism" in UK history.

He added that "no amount of trade deals with New Zealand are going to replace that we do at the moment with our big European neighbours".

His attack came after Sir John Major had accused Mrs May of making another Scottish independence referendum more likely with her 'hard Brexit' stance.

He also warned that Britons were being presented with an "unreal and over-optimistic" picture of the realities of leaving the European Union.

His comments led to a furious response from senior pro-Brexit Tories.

Iain Duncan Smith, himself a former party leader, described Sir John as “strangely bitter” and “rather sad”.

Foreign Secretary Boris Johnson tried to laugh off the rows as he said that he disagreed with his "old mate" Mr Osborne.

He predicted that the UK would strike a "fantastic" deal with the EU, although he acknowledged there could be some "bumps in the road" during Brexit talks.

But Brexit Secretary David Davis warned cabinet colleagues to prepare for what he said was the unlikely scenario that they would not secure an agreement.

Downing Street added that the Prime Minister had told her cabinet it was important not go into the negotiations with a "defeatist" attitude.

First Minister Nicola Sturgeon has called for Scotland to remain part of the Single Market even if the rest of the UK leaves.

Mr Osborne insisted that he was not "fighting the last war" but added that the " devil is in the details" of the post-Brexit deal.

Sir John has warned the diplomatic atmosphere is "sour" even before talks formally begin and has called for more “charm” from the UK Government.

Mr Johnson admitted that when he first met with other EU politicians after the Brexit vote "they were in a state of shock, some of them, puzzlement, they hadn't expected the outcome".

But, he added, "that mood has almost entirely vanished" and "they really want to help us and to do a great deal".

Meanwhile, Nissan confirmed that it could still review its position in the UK, despite assurances from Tory ministers.

Colin Lawther, the car maker's Vice-President, warned MPs that a failure to do a trade deal with the EU, which could lead the UK to adopt World Trade Organisation rules, would be “disastrous.”

The company employs 7,000 people at its Sunderland plant.

Meanwhile, Home Secretary Amber Rudd moved to try to stem an expected rebellion in the Lords on whether EU nationals will be allowed to stay in the UK after Brexit.

She has written to peers to say that the status of EU migrants will be at the top of the Government’s Brexit talks agenda with Brussels.

Some peers are predicting that the government will be defeated on the issue, the first major headache for the Government’s Brexit Bill.

Lib Dem leader in the Lords Lord Newby said that it was disgraceful that MPs had “so far allowed the Government to get away with their plan to unfairly use EU nationals as bargaining chips in upcoming Brexit negotiations”.

There were also warnings that the UK could face new limits on security co-operation with the EU after Brexit.

Britain's European commissioner Sir Julian King, who is responsible for issue at the commission, said the UK and the remaining 27 member states shared an interest in reaching an agreement that would replicate the existing arrangements as far as possible.

But he said that reaching such a deal would not necessarily be straightforward.