Theresa May has chosen to “appease” Brexit-backing right-wing newspapers rather than seek the best exit deal for Britain, Lord Mandelson has alleged.

The former Labour Cabinet minister and EU commissioner tore into the Prime Minister’s EU strategy ahead of her landmark speech – also accusing her of ducking “difficult choices”.

And he suggested a damaging split was opening up between Ms May and her Chancellor over her apparent determination to leave the EU’s single market and customs union.

In contrast, Ukip leader Paul Nuttall hailed her promise to make a clean break with the EU, saying: “I like what I’m hearing from her speech.”

Today, the Prime Minister is expected to confirm that she is steering Britain to what it widely seen as a ‘hard Brexit’, although she refuses to recognise the term.

But Lord Mandelson said she could have made different choices, which would not have threatened British businesses with losing access to “our biggest export market”.

“She would have had to face her Brexit backbenchers and her cheerleaders the Daily Mail or The Sun etc,” he said.

“And she has chosen to appease them rather than, in my view, to get the best deal for Britain.”

Both “the Chancellor and many other members of the Cabinet” were opposed to leaving the single market and customs union, he said.

Lord Mandelson also ridiculed the Prime Minister’s refusal to accept the term hard Brexit, saying: “She is pretending that difficult choices that the Government has to make simply don’t exit.

“If she doesn’t know what a hard Brexit is, let me tell her what it is

“It’s when UK goods suddenly face tariffs of as much as ten per cent or more in our biggest export market. It’s when new custom barriers add cost and delay to exports, or we lose our markets

“A hard Brexit is when financial and other services can’t access the EU market because EU regulators don’t accept the equivalent of the new UK regulatory regime.

“It’s when essential staff needed to fill vacancies in London from elsewhere in the EU are not able to come here – this is what a hard Brexit is about.”

Lord Mandelson said the EU was open to new immigration rules if Ms May would only listen, adding: “Reform of freedom of movement is certainly in the air in Europe.”

The comments, to BBC Radio 4’s Today programme, came ahead of a speech in which Ms May will finally try to kill off criticism that she lacks a workable Brexit strategy.

She will set out a list of 12 “negotiating priorities” for the withdrawal talks and shed new light on the critical questions of single market and customs union membership.

The Prime Minister will say: “We have 12 objectives that amount to one big goal: A new, positive and constructive partnership between Britain and the European Union.

“And, as we negotiate that partnership, we will be driven by some simple principles. We will provide as much certainty and clarity as we can at every stage.