91Èȱ¬

Boris Johnson must not be allowed to "mark his own homework" over an investigation into renovations at his Downing Street flat, Labour has said.

The Tory Party is facing an Electoral Commission inquiry over claims a donor initially covered the costs.

Separately, the PM's standards adviser Lord Geidt is examining whether Mr Johnson needs to declare any donations.

But Labour says Lord Geidt is not fully independent because the PM can ignore his findings.

Speaking on a visit to Manchester, Labour leader Sir Keir Starmer said "the idea of having an adviser who can investigate only if the prime minister says so just shows how weak the system is" and he called for a "proper, independent commission" to look in to the controversy.

Lord Geidt was unveiled as the PM's new standards adviser on Wednesday, replacing Sir Alex Allen, who quit five months ago after a dispute with Mr Johnson over a report into alleged bullying by 91Èȱ¬ Secretary Priti Patel.

Downing Street said the adviser role had "always been a direct appointment of the prime minister under successive administrations", adding that "the same process has been followed here."

The role has been beefed up, to make it more "pro-active", the government says, but the prime minister remains the "ultimate arbiter" of ministerial behaviour, including his own.

The Electoral Commission - the watchdog overseeing political finances - has launched an investigation which will assess the Conservative Party's compliance with laws on political donations.

It said there were "reasonable grounds to suspect that an offence or offences may have occurred".

A Conservative Party spokesman said: "We believe all reportable donations have been transparently and correctly declared and published by the Electoral Commission."

The prime minister receives a public grant of £30,000 per year to cover renovations at his Downing Street flat.

But newspaper reports suggest the bill for the latest work could be as high as £200,000.

Mr Johnson has said he paid the costs himself, but he has not specified whether this happened when he first received the bill, or whether he was loaned the money and later repaid it.

Normally, MPs have to register within 28 days any donations or loans which could influence their actions - and there is a list of ministers' interests with separate reporting rules.

The government insists the prime minister "acted in accordance with the appropriate codes of conduct and electoral law".

It has said Lord Geidt will look into the "facts surrounding" the renovation and will advise the PM on "any further registration of interests that may be needed".

But Mr Starmer said the situation was becoming "farcical" and the prime minister could deal with questions about who funded the refurbishment of his Downing Street flat "very, very quickly".

He said: "All he's got to do is answer a very simple question; which is who paid, initially, for the redecoration of your flat?

"The prime minister could actually end this now, tell us who paid for it in the first place, answer the question, it would take him about one minute and then he can get back on with the day job."

The FDA senior civil servants' union is currently taking legal against the government over its stance on the ministerial code.

It argues that decisions made under it should be subject to appeal in the courts - but the government says the code is separate from the law and should remain so.

FDA general secretary Dave Penman told the 91Èȱ¬: "The prime minister has ensured that not only is he the final arbiter of any investigation, but he retains the veto on whether an investigation starts in the first place."

He added: "Few will take comfort from his retention of almost complete control of the process."