Liz Truss dismisses Dominic Cummings claims as 'tittle-tattle' - as Labour demands inquiry

Lord Barwell The Cummings war could be 'extremely destabilising'

Mr Case's office argues that the inquiry into who leaked plans for a second national lockdown in October is ongoing and nobody has been exonerated.

"You've got the former most senior adviser to the prime minister saying he's fallen well below the standards of integrity that are needed for the office of the prime minister".

Mr Cummings claimed he advised the PM his flat renovation plans were "unethical, foolish, possibly illegal and nearly certainly broke the rules on proper disclosure of political donations if conducted in the way he intended".

After Downing Street named Johnson's former chief advisor, Dominic Cummings, as the source of leaks about the prime minister, Cummings hit back on Friday, denying he was the source and casting Johnson as incompetent and lacking in integrity.

Britain's opposition Labour Party on Saturday called for an investigation into how Prime Minister Boris Johnson funded a refurbishment of his Downing Street flat following claims by his former top adviser.

"What we need is a proper independent inquiry that isn't about two boys fighting and is about taxpayers", she added.

The disclosure is likely to further anger Mr Cummings who released his onslaught after he was accused by No 10 of a series of damaging leaks including text message exchanges between Mr Johnson and the entrepreneur Sir James Dyson.

Labour's shadow home office minister Jess Phillips described the public feud between Mr Johnson and Mr Cummings as "scrapping between two very powerful men who seem more interested in who's lying about what and who's leaking what than about the substance of the issue".

In an incendiary blog post, Mr Cummings went on to say that Mr Case had told Mr Johnson that neither he nor the then No 10 director of communications Lee Cain was the culprit.

It follows Mr Cummings' dramatic departure past year from No 10 amid the fallout of a bitter internal power struggle with Ms Symonds.

Johnson's office has said the government had followed the rules over the refurbishment.

A No 10 spokesperson said: "At all times, the government and ministers have acted in accordance with the appropriate codes of conduct and electoral law". What people want to know is that in line with the rules the prime minister has met the cost of this refurbishment.

Trade Secretary Liz Truss, told the BBC's Andrew Marr Show on Sunday that Mr Johnson covered the renovation costs for his Downing Street flat "from his own pocket".

Donations and loans to political parties of more than £7,500 must be reported to the Electoral Commission, which said it was having "discussions with the Conservative Party", but had not yet launched an investigation.

Earlier Labour also called for an independent commission on ethics and standards in government to be set up.

The government said "due diligence is carried out on every contract".