Margot James says she could not campaign for a no-deal Brexit under Boris Johnson

Margot James, who resigned as a minister to oppose a no-deal Brexit, has expressed concern that Boris Johnson’s cabinet represents a “massive shift to the right”, and refused to rule out quitting the Conservative party.

In an interview with the Guardian, the MP for Stourbridge said the new prime minister’s decision to pack his top team with veterans of the leave campaign confirmed his single-minded focus on leaving the EU on 31 October come what may.

“The best I can say is, I think we know where we are. Boris Johnson has been very decisive and very clear, and I know his start will go down very well with the people in my party who voted for him. And he’s thrown down the gauntlet by creating a government which is a massive shift to the right, and to a hard Brexit,” she said.

James, a former businesswoman, was creative industries minister before quitting earlier this month to support an amendment making it harder for a new PM to prorogue parliament to force through a no-deal Brexit.

Q&A Who sits in Boris Johnson's first cabinet? Show Hide The following people are in Boris Johnson's first cabinet: Sajid Javid, chancellor

Dominic Raab, foreign secretary

Priti Patel, home secretary

Michael Gove, chancellor of the Duchy of Lancaster

Robert Buckland QC, lord chancellor and justice secretary

Stephen Barclay, Brexit secretary

Ben Wallace, defence secretary

Matthew Hancock, health secretary

Andrea Leadsom, business secretary

Liz Truss, international trade secretary

Amber Rudd, work and pensions secretary

Gavin Williamson, education secretary

Theresa Villiers, environment secretary

Robert Jenrick, housing secretary

Grant Shapps, transport secretary

Julian Smith, Northern Ireland secretary

Alister Jack, Scotland secretary

Alun Cairns, Wales secretary

Baroness Evans, leader of the House of Lords

Nicky Morgan, DCMS secretary

Alok Sharma, international development secretary

James Cleverly, party chair and minister without portfolio These people also attend full cabinet meetings: Rishi Sunak, chief secretary to the Treasury

Jacob Rees-Mogg, leader of the House of Commons

Mark Spencer, chief whip

Geoffrey Cox QC, attorney general

Kwasai Kwarteng, energy minister

Oliver Dowden, paymaster general and minister for the Cabinet Office

Jake Berry, minister of state at the Cabinet Office

Esther McVey, housing minister

Jo Johnson, universities minister

Brandon Lewis, security minister

She said she could not have served under Johnson, given his commitment to the 31 October deadline, and would not be able to stand again as a Conservative MP if he were to campaign on a no-deal platform at the election.

“I wouldn’t say that I couldn’t canvass for Boris if the policy platform sat OK with me. I still feel that he’s been elected by the party and deserves a chance. Yes, I do feel that. And even though he didn’t rise to the position of foreign secretary, maybe he will rise to the position of prime minister,” she said.

But if the manifesto was to leave the EU without a deal, “I certainly wouldn’t campaign for that”, she said.

“I’m still hopeful he will get a deal, and he will get sufficient change to get it through parliament. But until he shows he’s done that, the jury’s out,” she added.

Play Video 2:07 Boris Johnson's first statement as PM to the House of Commons – video highlights

As Johnson appointed a series of rightwingers to his No 10 operation and cabinet, James also raised concerns that some of the “shady people” around him and some of those who “funded the original referendum campaign” would want to take the administration in the direction of slashing corporate taxes and regulations.

“There is a cadre of owners of large private companies who want Brexit because they want a low-tax, low-regulation economy,” she said.

James said any relaxation in the pace of deficit reduction should go towards funding public service priorities such as policing and social care rather than sweeping tax cuts. “It worries me about the country because I don’t think they’re the right policy goals,” she said.

The former business and media minister said there was no benefit to a no-deal Brexit, and criticised “arrogant politicians, most of whom have never been in business, or run a business, to think that they know better than the people running companies in this country”.

James is one of the senior Conservative MPs who resigned before Johnson took office and made clear they would fight a no-deal Brexit, saying she now felt freer to “resist the Steve Baker vision of the world” on a cross-party basis.

The former chancellor Philip Hammond, ex-justice secretary David Gauke and former development secretary Rory Stewart were among those who made clear they would not serve under Johnson. They are expected to join the ranks of vocal rebels on the Tory backbenches.

James denied earlier this week that she could be on the brink of defecting to the Liberal Democrats. But asked whether she could quit the party like Nick Boles, who is now an independent, she said: “I am really going one month at a time now. My goal is to make sure we leave in an orderly way with a negotiated settlement. And the other goal is to make sure we do not leave as the legal default implies without a deal.

“I wish to achieve those goals with minimum damage to my party. A lot more colleagues are thinking more about what is in the national interest.”

James refused to say whether she was one of those Tory MPs – like Hammond and Dominic Grieve – who would countenance voting down a Johnson administration pursuing no deal, even if it could trigger a general election.

Asked if she would face a difficult decision, she said: “Very. I’m not at the moment prepared to answer that question. If you’d asked me that question six months ago it would have been completely unthinkable. One can posit all these Doomsday scenarios so I’ve decided I’m not going to answer the question.

“Most MPs are clear they would all support the government come what may. Then there is a very small minority in which they say there are circumstances in which they couldn’t. I’m kind of in between. I would find it very hard and I’m hopeful that other means will be found. Most of all, I’m hopeful most of all that Boris will tone down his Brexit policy.”

Quick guide 10 Boris Johnson leadership campaign pledges - and their costs Show Hide 1: Raising the 40% income tax threshold Cost: £9bn. Only 12% of people in the UK earn more than £50,000 a year, so this pledge to move the 40% threshold up to £80,000 would help those on the highest incomes. 2. Increasing the starting point for national insurance contributions to £12,500 Cost: £11bn. At present people pay NICs when they earn £166 a week and income tax when they earn £12,500 a year. Johnson wants to gradually align the two systems by raising the NICs ceiling to an annual £12,500. 3. Raise education spending Cost: £4.6bn. Theresa May’s successor says he will raise education spending to £5,000 for every secondary school pupil and £4,000 for each primary school pupil. 4. More police Cost: £1.1bn. Johnson has promised an extra 20,000 officers. 5. Free TV licences for the over-75s Cost: £250m. This would reverse the BBC - and George Osborne's -decisions over this perk for pensioners. 6. Raising the level at which stamp duty is levied Cost: £3.8bn. There have been reports that the incoming prime minister would like all house sales under £500,000 in England, Wales and Northern Ireland to be exempt from stamp duty. 7. Nationwide full fibre broadband coverage by 2025 Cost: unknown. Industry experts say this is not feasible in the time available, given coverage is currently less than 10%. 8. The creation of six free ports in the UK Cost: unknown. Johnson said while on the hustings with Jeremy Hunt that he intended to create “about six” free ports – zones designated by the government to pay little or no tax in an attempt to boost economic activity. 9. Review HS2 and build HS3 Cost: unknown. One of Johnson’s big early decisions will be whether to scrap HS2 and spend the money on alternative rail infrastructure such as linking the big cities of the north through HS3. Any savings generated by scrapping HS2 will almost certainly be recycled into other transport projects. 10. Raising the national living wage Cost: unknown. The government employs one in six of the people working in the UK, so it would be affected by Johnson’s promise to raise the national living wage. Larry Elliott Economics editor

However, she said no one could predict whether the new PM was prepared to disappoint hardline Eurosceptics, to whom he has made a promise to scrap the backstop and strike a completely new deal with Brussels.

“Boris uses a lot of language. We don’t know yet whether he is able to adjust his style, or whether he even wants to – but it’s what my father would call ‘loose talk’. I think it comes from the war: ‘Loose talk costs lives.’ It’s unsubstantiated, quickly backtracked from words, that sound good the moment you use them. His campaign has been full of that – and maybe he will change. So we don’t know yet,” she said.

James said she believed about 25 Conservative MPs might be prepared to vote against no deal once resignations from Johnson’s government were complete.

And she was cryptic about the possibility of Tories joining Labour and Lib Dem MPs to form a government of national unity to avoid no deal, amid several reports that preliminary talks were already happening.

“I am aware I’m on the record, so I’m not going to comment on that,” she said.