Cabinet ministers believe there is now a real risk of a no-deal Brexit, with sources close to them describing the mood in government as depressing and No 10 as “run by lunatics”.

Senior members of the cabinet from both sides of the Brexit argument are understood to think the chances of the UK leaving without a deal have substantially increased after the prime minister set herself against a longer extension to article 50.

One aide to a cabinet minister said No 10 was in “full-on bunker mode” and the prime minister’s speech from Downing Street showed “they have all taken leave of their senses”.

Another soft Brexit cabinet source described the mood as “depressing” and said of no deal: “The risk is now very real.”

On the other side, one leave-supporting cabinet minister believes May has no intention of resigning if her deal fails to pass next Tuesday and that she would prefer to switch to a position of supporting no deal rather than allow a longer extension to article 50. They point to the fact that 63% of Conservative MPs opposed a delay to Brexit and opinion polls suggesting a shift in public opinion towards no deal.

In this scenario, the prime minister could attempt another meaningful vote next Thursday in a high-stakes gamble that would challenge MPs to back her deal or face no deal at the last minute.

On Thursday, Liz Truss, a Treasury minister who sits in cabinet, told the Sun that she did not believe the “plague of locusts stuff” around leaving without a deal, adding: “I believe No Deal is better than a long extension.”

Before calling yet another vote, the government would either have to persuade John Bercow, the Speaker, that it was presenting a materially different deal to the Commons or overturn standing orders that prevent the same motion being repeatedly put to MPs.

The alternative at this point would be that parliament could potentially decide to revoke article 50 – but it is unclear how and whether that would be legally binding.

Some Labour MPs who fear a no deal are taking comfort from a leaked briefing note prepared for Kwasi Kwarteng, a Brexit minister, which said that if the vote fails then “MPs will have to decide how to proceed”.

Cabinet members Jeremy Hunt and Liam Fox leave Downing Street. Photograph: Jack Taylor/Getty Images

They also point to a speech made by May in the House of Commons on 26 February in which she said: “We would only leave without a deal with the consent of parliament.”

However, there is little sense that the group of cabinet ministers opposing a no-deal Brexit have yet come up with a plan to stop it happening if May does change her mind.

Behind the scenes, there was fury among Tory MPs – and even the whips – about May’s speech blaming parliament at a time when she needs more votes to pass her Brexit deal.

MPs said relations between the whips and No 10 have broken down since the chaos of last week’s votes, with ITV reporting that the chief whip, Julian Smith, had been sympathising with colleagues that Wednesday night’s speech was “appalling”. A source close to Smith later said: “The chief whip is supportive of the PM’s statement and understood her desire to address the nation directly.” Downing Street declined to comment.

Nick Boles, the Conservative MP leading efforts for a cross-party soft Brexit, joked that the speech was an example of: How to Win Friends and Influence People by Theresa May.

The Conservative MP Sam Gyimah, who resigned as a minister over the withdrawal agreement, accused May of trying to blackmail MPs. “I think democracy loses when a prime minister who set herself against the House of Commons then blames MPs for doing their job,” he told the BBC.

One middle-ranking minister said “everyone is upset about it” and described it as the “completely wrong” approach at at time when she should be reaching out.

One source close to a cabinet minister said Downing Street was “run by lunatics” and blamed communications director Robbie Gibb for the decision to allow May to speak directly to the nation pitting MPs against the public.

A Downing Street spokeswoman would not comment on that claim, and when asked for a response to the angry reaction of Conservative MPs, she said: “The message was aimed at the public.”

Following the speech, there is degree of hopelessness among Conservative MPs because they have no idea what May plans to do next, beyond predicting that she will not resign willingly.

Chris Wilkins, a former speechwriter for May, said that he thought she was finally running out of road as prime minister. However, he did not expect her to resign because of her dogged determination to carry on with her duties: “I think that if the entire cabinet resigned, she would not go because in her mind she cannot be forced out under party rules. If there was a cabinet of one, she would sit in it.”

The ex-No 10 aide added that he believed May’s televised address was a mistake because it attacked parliament at a time when she needed its support. It was characteristic of her core beliefs that “I’m the one who is the grownup” and that many other MPs did not undertake their jobs with sufficient seriousness, he added.

“One thing she says frequently is that ‘politics is not a game’. Others may be frivolous but in her mind she is the one who gets on with the job,” Wilkins said.

It is understood that May carried on as if it was business as usual in meetings with senior Brexiters, including Boris Johnson, over the weekend and earlier this week, talking as though she would be continuing in office and promising a restructure of the Department for Exiting the EU at the next stage of negotiations.

Those MPs who have been in to Downing Street in the past week have been surprised by May’s resilience and intransigence despite the intensity of the crisis, giving one visitor the impression that she would be prepared to lead the Conservative party into another general election if it came before her stated departure date of 2022.

Publicly, May was supported by Jeremy Hunt, the foreign secretary, who toured the broadcast studios to say that she had been frustrated by the need to delay Brexit and that she was “under extraordinary pressure”.

However, others sounded less supportive. When asked if the prime minister had been wise to set herself against MPs, Sajid Javid, the home secretary, told reporters in Essex: “I’ve just come from Westminster to get away from Brexit, so I don’t think it’s appropriate to answer that question.”