The next year will see a fresh Brexit crisis, parliament sidelined and a renewed threat to the union – but there is still hope for supporters of progressive politics, according to some of the leading figures who took on the government over Brexit.

The 80-strong majority secured by Boris Johnson at the election ended the parliamentary stalemate that left the prime minister unable to push through his Brexit deal. The election also ended the tenures of key figures responsible for leading the battle to oppose his plans.

The Observer spoke to David Gauke, who quit the cabinet; Sam Gyimah, who defected from the Tories to the Lib Dems; Anna Soubry, who set up a new party; and Dominic Grieve, who helped lead the fight against Brexit in parliament, about the crucial year ahead. They pointed to key contradictions in Johnson’s plans that could lead quickly to a Brexit crisis – and predicted he would not pivot towards securing a soft Brexit trade deal with the EU.

Gauke said Johnson was now in an enormously strong position, with parliament unable to curb his plans. However, he said the prime minister now faced the problem of delivering Brexit without inflicting further pain on the very areas, such as the Midlands and the north-east, that delivered him a majority.

“To what extent is he going to deliver a purist form of Brexit, or is he going to look to find a pragmatic way forward that ensures our economy can grow?” he said. “I would have thought the more likely course of action for him is to keep beating the Brexit drum and blame any difficulties on the EU and appear defiant. His determination to diverge makes it hard to see common ground. I hope some kind of pragmatic compromise is the way forward, but given how boxed in he is on the implementation period not being extended and an apparent determination to reject any kind of dynamic alignment, I think we may well find ourselves at the end of 2020 facing real problems.

Boris Johnson is likely to blame the EU for any difficulties in forging a deal, says David Gauke. Photograph: 10 Downing Street/AFP via Getty Images

“The part of the country that is likely to be worst hit by a hard Brexit is the north-east of England, an area that has voted Conservative in a way that is unprecedented. That’s going to make it hard … If you haven’t got a strong economy that gives you the money to spend on the north of England, then it will be very hard to square the circle.”

Gyimah agreed: “Bumper-sticker slogans like ‘take back control’ and ‘get Brexit done’ may unite different tribes for the purposes of a campaign, but their interests are not aligned. The faultlines that run through Brexit are as real as ever.

“There are painful trade-offs ahead, which will affect every sector and every constituency in the country in different ways. An 80-seat majority cannot deny this reality, nor can you use pork-barrel politics to blunt the edge of every hard Brexit policy decision. Most of those new MPs will have some tough explaining to do to their constituents as the rubber hits the road. And a slower-growing economy means less money for public services, and a new era of self-imposed austerity.”

The prospect of securing a good trade deal at the end of 2020 was very uncertain, said Grieve. “One of the themes of the election that continues to be of great concern to me is the risk of ending up with either a very unsatisfactory deal or no deal at all. I think they are very considerable.”

He also predicted a new constitutional crisis as Brexit takes place. “If the border in the Irish Sea starts to materialise, then I can foresee that politics in Northern Ireland will become very heated up,” he said. “That has been underestimated, quite apart from the fact that it may also lead obviously to a rise on the other side for a demand for a border poll. With Scotland, the SNP have the grievance to revive the call for independence. How is that going to be contained? It is containable for a while, but I’m not sure it is if the SNP get a majority in the 2021 Scottish parliamentary elections.”

Soubry, who quit the Tories in February to start the Independent Group for Change, called on Tories who had privately expressed concerns about Johnson’s approach to speak out. “You do have to say, where are these people that sat in meetings with the likes of me and Dominic Grieve, Antoinette Sandbach, who put the people’s interests before their own. Where are they now? What are they going to do? Are they going to sit on their hands and stay mute?”

Anna Soubry believes there is still potential for a new progressive party to emerge. Photograph: Jacob King/PA

However, Soubry said that despite the failure of her new party, there was still the potential for a new progressive party to emerge should Labour continue to be embroiled in civil war. “The Tory party will get its comeuppance in due course,” she said. “The tragedy is that unless the Labour moderates do the brave and right thing and leave to form a new centre-ground party, then the Tory party will be in power for at least 10 years, unchecked and unopposed. We were always the unofficial opposition. We were a genuine coalition. It was the David Lammys, the Dominic Grieves, it included the Lib Dems and SNP. We were hugely effective at checking the excesses.

“All those people who were part of the much bigger grouping that cometh the hour didn’t have the courage [to leave Labour], if they now want to do that. And if the Lib Dems recognise that they too have to change … and accept that there must be a different way of doing politics – if those things happen, then we could rebuild the centre ground of politics as we tried to do in February and failed. But it relies on people being brave and honest. I’d be more than happy to play my part in that.”

Liberal voters are going to have to live with the fact that there is no proper opposition to the prime minister Dominic Grieve

Gyimah urged liberals to “resist the idea that the size of the majority means the case for progressive politics has been lost”. He added: “Britain now needs a new narrative that looks to the future and progressive voices must be a part of forging it. I continue to believe passionately that we need a progressive centre. If we’re serious about winning this battle for the future, tribalism on the progressive left has to end … This fight won’t be won in the next news cycle. We can win it, because populists eventually get found out. The wheel of history will turn again and we must be ready.”

Grieve is less optimistic. “Liberal voters are going to have to live with the fact that there is currently no proper opposition to the prime minister,” he said. “I think we’re in for a period where opposition to what Johnson is doing is going to be very difficult to put together. I was just looking at a letter sent to me this morning that contains the words, ‘God for Boris, England and St George! We will take the Brexit hill, Mr Grieve. It is there in our history.’ There will be a lot of people who will be let down if God for Boris, England and St George doesn’t succeed.”