THE Government will do "whatever we have to" to ensure Britain stays competitive if it is shut out of the EU single market after Brexit, Chancellor Philip Hammond has warned.

As Theresa May prepared to lay out her approach to the Brexit negotiations in a keynote speech on Tuesday, Mr Hammond hinted the Government was ready to push through aggressive cuts to business taxes to ensure UK-based firms remained competitive in the face of EU tariffs.

In an interview with the German Welt am Sonntag newspaper, the Chancellor said while he was "optimistic" a reciprocal deal on market access could be struck, he was not going to "lie down" and accept it if it was "closed off".

"I personally hope we will be able to remain in the mainstream of European economic and social thinking. But if we are forced to be something different, then we will have to become something different," he said.

"If we have no access to the European market, if we are closed off, if Britain were to leave the European Union without an agreement on market access, then we could suffer from economic damage at least in the short-term.

"In this case, we could be forced to change our economic model and we will have to change our model to regain competitiveness. And you can be sure we will do whatever we have to do.

"The British people are not going to lie down and say, too bad, we've been wounded. We will change our model, and we will come back, and we will be competitively engaged."

His comments came amid fresh reports Mrs May is preparing to set out plans for a "hard Brexit" when she delivers her speech at Lancaster House - pulling out of the single market and the customs union in order to regain control of immigration and end the jurisdiction of the European Court of Justice.

While Downing Street would not be drawn on the claims, The Sunday Telegraph quoted a government source as saying: "She's gone for the full works. People will know when she said 'Brexit means Brexit', she really meant it."

The comments alarmed pro-Remain MPs. Former education secretary Nicky Morgan, who was sacked by Mrs May, said the Prime Minister should put "maximum participation" in the single market at the heart of her negotiating strategy and warned her not to do anything to damage the economy.

"The Government will be doing a disservice to the country and to both Leave and Remain voters if it dogmatically pursues a hard, destructive Brexit where immigration control is the be all and end all, our economy is undermined, and people are left poorer," she said.

Writing in The Sunday Times, Brexit Secretary David Davis said the Government would be seeking to forge a "strong new partnership" with the remaining 27 member states.

"We don't want the EU to fail, we want it to prosper politically and economically, and we need to persuade our allies that a strong new partnership with the UK will help the EU to do that," he wrote.

He also indicated that the Government would consider some form of transitional arrangement - a move likely to be regarded with suspicion by hardline Brexiteers who have been demanding a clean break.

"If it proves necessary, we have said we will consider time for implementation of the new arrangements," he said.

One of the themes of Mrs May's speech is expected to be the need to foster unity by building "common goals" - such as protecting and enhancing workers' rights - in an attempt to create a consensus after months of acrimonious exchanges.

Most attention, however, will inevitably be centred on her approach to key issues around the single market, the customs union and free movement of labour.

It is unclear however how much detail the Prime Minister will be prepared to reveal at this stage, having repeatedly stressed that she is not going to undermine her negotiating position by giving away too much too soon.

Former Ukip leader Nigel Farage said he has yet to be convinced by Mrs May's Brexit strategy.

The MEP told Sophy Ridge on Sunday on Sky News: "I'm quite certain Theresa May will do what she always does - sound very reassuring, she will look to be very much in control, saying all the right things and people like me will say it sounds great but why is it taking so long?

"When it comes to immigration, in particular, which she is highlighting, this is coming from the person who was home secretary and failed completely.

"I'm yet to be convinced, I have to say."

Liberal Democrat leader Tim Farron, who reiterated he does not believe freedom movement arrangements should change, claimed Mrs May is starting the Brexit process by "waving the white flag" over single market membership.

He told BBC One's Sunday Politics: "I certainly take the view that heading for a hard Brexit, essentially that means being outside the single market and the customs union, is not something that was on the ballot paper last June.

"For Theresa May to adopt what is basically the Nigel Farage vision of Britain's relationship with Europe and the rest of the world is something that was not voted for last June.

"I think it's right for us to stand up and say that a hard Brexit is not the democratic choice of the British people and we should be fighting for the people to be the ones who have the say at the end of this process, not have it forced upon them by Theresa May and David Davis."