Theresa May should deliver Brexit and then resign so a new generation of Tory MPs can shape the UK’s future with the EU, her ex-policy chief has said. 

As competing visions for post-Brexit Britain continue to divide the Conservatives, George Freeman has warned of “a danger in Parliament of a real crisis” this winter amid reports of a plot to topple the prime minister. 

His comments come after hardline Brexiteers this week openly discussed ways of unseating May. 

Around 50 MPs are understood to have discussed ways and means of getting rid of the PM at a gathering of the European Research Group (ERG). 

Freeman told BBC Radio 4′s Today programme: “I think they [opponents to May] risk making Parliament, the Conservative Party and the prime minister look shambolic.

“I think we should let the prime minister get Brexit over the line at the end of March and leave the longer-term debate about what our new relationship is to a new-generation leader.”

Freeman, who previously headed up No 10′s policy unit, said he had not discussed his proposals with the PM but insisted that a leadership contest need not be “chaotic”.

He added: “I believe very strongly that the prime minister’s instincts are right on this. We have to implement the people’s demand to leave the EU but how and where that leaves the country in the world and the longer-term relationship is an issue that I think should be shaped by, for and in the spirit of a new generation.”

In order to win the trust of younger people who feel that Brexit is “being forced on them”, he said Tories must make clear that EU withdrawal “won’t be a Nigel Farage Brexit, we are going to make it a One Nation Conservative Brexit and we are going to shape it and recast it in the spirit of a new generation”.

His interview follows an event in London on Thursday night hosted by The Times, in which Freeman told the audience: “I think we need a new energy, new direction, a new generation leader to take this forward, backed up by the talent that we’ve got.

“If I was still advising Theresa May, my advice would be to frame it in those terms – seal the deal for a new generation and hand the torch of responsibility on to them and I think the country would cheer.”

Freeman, MP for Mid Norfolk, also appeared to suggest high-profile figures such as Boris Johnson and Michael Gove should not be in the frame to take over.

He added: “I think it’s quite difficult for some of the glittering talent that we have at the top of our Cabinet to be the force of renewal and I think it needs to be led by somebody with a new mandate.

“I think anyone who was involved in that referendum campaign – I think it was a bad campaign on both sides – they’re bound by all sorts of promises that shouldn’t have been made, they carry the baggage of a terrible process.”

Last month, however, May insisted she was “in this for the long term” as she faced questions over the prospect of the former foreign secretary launching a bid for power.

She said: “I’ve been asked before whether it’s my intention to lead the Conservative Party into the next general election, I answered that question before – I’m in this for the long term.

“What I’m focusing on doing is delivering what the British people want – the British people voted for us to leave the European Union and I and the government will be delivering that.

“But what I’m also focused on doing is delivering on the domestic agenda which is of concern to people.”