The Daily Telegraph claims that chief medical officer Professor Sir Chris Whitty had told Mr Hancock in April 2020 that there should be testing for "all going into care homes and segregation whilst awaiting a result".

But the leaked messages suggest Mr Hancock rejected that advice, telling an aide that the move "muddies the waters", instead introducing mandatory testing just for those coming from hospitals.

According to the investigation, he said: "Tell me if I'm wrong but I would rather leave it out and just commit to test and isolate ALL going into care from hospital.

"I do not think the community commitment adds anything and it muddies the waters."

He also expressed concerns that expanding care home testing could "get in the way" of the 100,000 daily test target he wanted to hit, the investigation said.

Mr Hancock is considering legal action against the Telegraph as his spokesman said claims he rejected clinical advice on care home testing was "flat wrong" because he was told it was "not currently possible" to carry out the tests due to a lack of capacity.

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Labour leader Sir Keir Starmer said families whose loved ones died of COVID will view the leaked messages as an "insulting and ghoulish spectacle" and the "country deserves better" as he called on Rishi Sunak to ensure the official COVID Inquiry has no more delays.

Reacting at Prime Minister's Questions, hours after the story broke, Mr Sunak insisted the official inquiry is the "right way" to investigate the government's handling of the pandemic rather than relying on "piecemeal bits of information".

The messages were leaked by journalist Isabel Oakeshott, who received them while working on Mr Hancock's Pandemic Diaries memoir.

She said she was releasing them because it would take "many years" before the official COVID inquiry is completed and "we absolutely cannot wait any longer for answers".

Inquiry chair Lady Hallett insisted the inquiry "will not drag on for decades" and "there will be no whitewash" as she began proceedings on Wednesday.

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'I want to hit my target'

Also included in the messages:

• In September 2020, during a test shortage, one of Mr Hancock's advisers helped to send a test to the home of senior Tory Jacob Rees-Mogg for one of his children.

• As he struggled to meet the testing target, Mr Hancock texted former Tory chancellor George Osborne to ask for help.

He said the thousands of spare testing slots were "obvs good news about spread of virus" but "hard for my target".

Mr Osborne, editor of the Evening Standard until July 2020, had responded: "Yes - of course - all you need to do tomorrow is give some exclusive words to the Standard and I'll tell the team to splash it."

Mr Hancock had later added: "I WANT TO HIT MY TARGET!"

Hancock 'considering all options'

A source close to Mr Hancock said: "[Ms Oakeshott] has broken a legal NDA [non-disclosure agreement].

"Her behaviour is outrageous.

"Having not been approached in advance by The Telegraph, we have reviewed the messages overnight.

"The Telegraph intentionally excluded reference to a meeting with the testing team from the WhatsApp."

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"This is critical," the source added, "because Matt was supportive of Chris Whitty's advice, held a meeting on its deliverability, told it wasn't deliverable, and insisted on testing all those who came from hospitals.

"The Telegraph have been informed that their headline is wrong, and Matt is considering all options available to him.

"This major error by Isabel Oakeshott and The Telegraph shows why the proper place for analysis like this is the Inquiry, not a partial, agenda-driven leak of confidential documents."

Answering an urgent question from Labour on testing of care home residents during the pandemic, Health Minister Helen Whately told MPs the "importance of testing was never in doubt" but added "tough decisions about prioritisation had to be made".

"I should mention that selective snippets of WhatsApp conversations give a limited and at times misleading insight into the machinery of government at the time," she told the Commons.

"That is why the COVID inquiry is so important, so we have the right preparations in place to meet future threats and challenges."

A spokesman for Mr Hancock said: "It is outrageous that this distorted account of the pandemic is being pushed with partial leaks, spun to fit an anti-lockdown agenda, which would have cost hundreds of thousands of lives if followed. What the messages do show is a lot of people working hard to save lives."

He added: "These stolen messages have been doctored to create a false story that Matt rejected clinical advice on care home testing. This is flat wrong."

But the Telegraph's associate editor, Camilla Tominey, told the BBC: "The suggestion that we've somehow adopted these messages is simply not true."

The MP for West Suffolk, who came third in the most recent series of I'm A Celebrity... Get Me Out Of Here!, has already said he will stand down at the next general election.

Labour's shadow social care minister Liz Kendall said: "We need more humility and less celebrity from the member for West Suffolk and above all we need answers."