BORIS Johnson will decide himself if he has broken any rules over the refurbishment of his Downing Street flat, No 10 has revealed.

No 10 said this morning former private secretary to the Queen, Lord Geidt, was appointed as the new independent adviser on ministers’ interests. He will lead an investigation into the funding of the property revamp.

But the Prime Minister’s spokesman confirmed Johnson will remain the “ultimate arbiter” of whether he broke the ministerial code.

Johnson's spokesman said: "As the ultimate arbiter of the code, the responsible for deciding on an investigation and the drawing of final conclusions from it, rightly remains the responsibility of the Prime Minister. That's been the case under successive governments."

He added that the findings of the independent advisor would be published "in the normal way, as you'd expect."

Asked if Johnson would recuse himself, he said: "The code's very clearly set out on that, with regards the role of the Prime Minister in this, and that hasn't changed."

The post of ministerial standards adviser has been vacant since Sir Alex Allan resigned in November in response to Johnson standing by Home Secretary Priti Patel despite an investigation finding her conduct “amounted to behaviour that can be described as bullying”.

The appointment of the new adviser paves the way for the publication of the latest register of ministerial interests, which could contain details of any donations to fund the Downing Street flat.

Labour and the SNP have accused Johnson of having “lied” over the funding.

WATCH: SNP MP told language 'not savoury' as he asks Boris Johnson if he's a liar

Labour also accused senior members of the Government of a possible “cover-up” as ministers battled a series of “sleaze” allegations.

Prime ministers get a budget of up to £30,000 per year to renovate their Downing Street residency, but newspaper reports have suggested Johnson has spent up to £200,000.

Last week, the Daily Mail published details of an email from Tory peer Lord Brownlow in which he said he was making a £58,000 donation to the party “to cover the payments the party has already made on behalf of the soon-to-be-formed ‘Downing Street Trust’”.

Johnson was also facing pressure over allegedly saying in October he would rather see “bodies pile high” than impose a third coronavirus lockdown.

Keir Starmer challenged Johnson on the remarks at PMQs, asking for a categoric “yes or no” as to whether he made comments to that effect.

“No,” Johnson responded, before again being challenged on the remarks by the SNP’s Westminster leader Ian Blackford.

He said: “If he is going to relay that kind of quotation, it is up to him in a place like Parliament to produce the author, the person who claims to have heard it, because I can’t find them, he says that they’re willing to go [on] oath. Perhaps they’re sitting somewhere in this building, I rather doubt it because I didn’t say those words.”

Ian Blackford said: “The BBC and ITV have multiple sources confirming that this is what the Prime Minister said.

"People are willing to go under oath, Mr Speaker, confirming that the Prime Minister said these exact words. Under oath, Mr Speaker.

“Now, parliamentary rules stop me from saying that the Prime Minister has repeatedly lied to the public over the past week. But can I ask the question? Are you a liar Prime Minister?”

Johnson replied: “Mr Speaker, I’ll let it to you to judge whether the right honourable gentleman’s remarks were in order, but I will say to him –“

Speaker Lindsay Hoyle said while the comments were in order, they were “not savoury and not what we would expect”.

Johnson went on to say Blackford should be able to produce the authors of such statements if he wants to make claims like that in the House of Commons, and denied saying the comments.

The SNP representative responded: "Of course, it's the Prime Minister's behaviour which is not in order. This is a Prime Minister that's up to his neck in a swamp of Tory sleaze. 

"We've seen contracts for cronies, texts for tax breaks and cash for curtains. The Prime Minister has dodged these questions all week and he's dodged them again today. But these questions simply are not going to go away."

The bombardment of allegations around the Prime Minister come as he is embroiled in a public row with Cummings, who until last year was his senior adviser in No 10.

Cummings hit out at his former boss in a blog post, saying he had fallen “below the standards of competence and integrity the country deserves” after No 10 sources, reportedly the Prime Minister himself, accused him of being behind a series of leaks.