THERESA May’s attempt to relaunch her leadership around her first anniversary in office has been undermined by a fresh wave of speculation about her survival.

The Prime Minister will use a speech tomorrow to stress her “determination” to deliver Brexit and the programme of social reform she first announced a year ago in Downing Street.

She will say she has an “unshakeable sense of purpose” to build a stronger, fairer nation and her “commitment to change in Britain is undimmed”, despite losing her Commons majority.

She will say: “I am convinced that the path that I set out in that first speech outside Number 10 and upon which we have set ourselves as a government remains the right on.”

Acknowledging the election result was “not what I wanted”, she will try to reach out to other parties in the Commons by asking for ideas on tackling the country’s challenges.

“We may not agree on everything, but through debate and discussion… ideas can be clarified and improved and a better way forward found," she will add.

The SNP Government said that if she was serious about consensus she should give Scotland a seat at the Brexit negotiations.

However Mrs May's bid to reassert her authority before Thursday’s publication of the EU Repeal Bill has been hurt by a former cabinet minister saying she has to go.

Andrew Mitchell, a close friend of Brexit Secretary David Davis, a potential replacement for Mrs May, was reported saying she was “dead in the water”.

The former international development secretary, who was Mr David’s campaign manager for the Tory leadership in 2005, was reported to have told a group of Tory MPs his view on June 26, after Mrs May struck a deal with the DUP to keep her minority government afloat.

The Mail on Sunday quoted an MP at the One Nation Commons dining club saying: “Mr Mitchell effectively said she was dead in the water.

“He said she was weak, had lost her authority, couldn't go on and we needed a new leader. Some of us were very surprised and disagreed with him."

Mr Mitchell downplayed the remarks but did not deny making them, saying: “This is an overheated report of a private dinner conversation."

Grant Shapps, the former Conservative party chairman, also wrote in a newspaper article yesterday that Mrs May needed a “completely different model to remain in power” after relying too heavily on a team with a “dysfunctional, arrogant and corrosive attitude”.

Mrs May was criticised in her first year for being cut off in Number 10 by her feared special advisers, Nick Timothy and Fiona Hill, who quit after the election after being branded “toxic”.

Ms Shapps said: “During year one, and with a small majority, countless of her own MPs were left excluded and bemused, not having exchanged even a single word with the PM. During year two, Theresa May will need to operate a completely different model to remain in power.

“She must throw open Downing Street to welcome innovative ideas, listen to business and make better use of the party’s broad talent in parliament and further afield.

“Sharing power beyond a tiny Praetorian Guard may not be her instinctive approach, but doing so now could still help her go beyond just about managing the year ahead.”

There were also reports a small group of Tory MPs wanted Mrs May to quit ahead of the Tory party’s autumn conference, despite the risk of a general election that Labour might win.

Justice Secretary David Lidington said "summer parties" and “too much warm Prosecco” was behind the leaderhsip rumours.

He told the BBC's Andrew Marr Show: "Almost every July a combination of too much sun and too much warm Prosecco leads to gossipy stories in the media.

"The key thing is this: the public has had an election, I think they want the politicians to go away and deal with the real problems that the people of this country are facing."

Mr Lidington also praised the PM’s performance on Sky's Sophy Ridge On Sunday, saying: "I see somebody who is very determined to lead and get on with the job."

SNP Brexit minister Michael Russell said: “If the Prime Minister is genuinely interested in creating a consensus then Scotland should have a seat at the negotiations to leave the EU.

“The election result was a comprehensive rejection of Tory plans for an extreme hard Brexit. Single market membership, whether for the UK or Scotland, must now be back on the table.”