Sir Keir Starmer is under investigation for a possible breach of parliamentary rules after failing to declare that some of his wife’s high-end clothes were bought for her by his biggest personal donor, Lord Alli.

The Labour peer paid for a personal shopper, clothes and alterations for Lady Victoria Starmer, reportedly both before and after the Labour leader became prime minister in July, according to The Sunday Times.

This year, Sir Keir has received – and disclosed – nearly £19,000 worth of work clothes and several pairs of glasses from Lord Alli, the former chairman of online fashion retailer Asos, The Times reports.

In addition, the peer, whose personal wealth is estimated at £200m, spent £20,000 on accommodation for the now prime minister during the election and a similar sum on “private office” costs, which was also disclosed, the paper says.

A Labour Party spokesperson told Sky News it was an oversight that had been corrected after it “sought advice from the authorities on coming to office”. They added: “We believed we’d been compliant, however, following further interrogation this month, we’ve declared further items.”

The Tories called for a “full investigation” following The Sunday Times report.

A Conservative Party spokesman said: “It’s taken just 10 weeks for Keir Starmer to face an investigation for his conduct.

“After facing allegations of cronyism and now apparent serious breaches of parliamentary rules there must be a full investigation into the passes for glasses scandal.

“No doubt the millions of vulnerable pensioners across the country who face choosing between heating and eating would jump at the chance for free clothes just to keep warm in the face of Labour’s cruel cut.”

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Lord Alli’s involvement with the Labour leader has already proved controversial after it emerged he had been given a Downing Street security pass without apparently having a government role.

The revelations are awkward for the prime minister, who has promised to clean up politics.

Sir Keir, like all MPs, must declare any of his relevant interests under rules set up to protect politics from improper influence and uphold transparency.

The Times said the prime minister’s office approached the parliamentary authorities to make the late declarations last Tuesday.

His advisers were already in touch with them by then after several designers had approached Lady Starmer asking if she was interested in free products such as clothes, jewellery and make-up.

Staff had asked if the prime minister would need to declare his wife being given those items if she accepted and were told he would.

That prompted his team to ask if the previous gifts from Lord Alli should also have been declared on the same basis and it was decided they did.

They then wrote to the authorities to update the prime minister’s register of interests, which is scheduled to be published next month. Lady Starmer has separately declined to accept the offers from designers.