LONDON (AFP) - After lavishly redecorating their Downing Street flat, Prime Minister Boris Johnson and his wife Carrie now risk being homeless - and face calls to find a new venue for their wedding party.

The couple married in a secret ceremony in London in May 2021 and were limited to having 30 guests to a garden party in Downing Street afterwards because of Covid-19 restrictions.

They have been planning a more glamorous reception at Chequers, the prime minister's country retreat north-west of London, on July 30.

In announcing his resignation on Thursday (July 7), Johnson said he would stay in office until a new Conservative leader is elected in the coming months, possibly until October.

But the Daily Mirror, Guardian and others reported that the timeline has more to do with his desire not to lose the perks of Chequers ahead of the bash, explaining that invitations had already gone out.

Critics said Johnson had the 16th century country home on his mind in his resignation speech outside 10 Downing Street, when at one point he misspoke in thanking "the wonderful staff here at Chequers".

"As much as we'd all like to have a lavish wedding at the taxpayer's expense in Chequers, he won't be able to do so because the British public will find it abhorrent," London mayor Sadiq Khan told LBC radio.

"And those decent Tories... will not accept a situation where is seeking to stay on as prime minister for his personal benefit, rather than the national interest," the opposition Labour politician said.

Chequers was already the subject of recent headlines over claims that the Johnsons wanted to build a treehouse there worth £150,000 (S$250,000) for their two-year-old son Wilf. They denied that.

But in another of the many scandals that have dogged his tenure, he had to repay tens of thousands of pounds for luxury wallpaper that he and Carrie used for a makeover of their government flat above 10 Downing Street.

The Johnsons now begin the search for a new home. They own at least two properties together, but one is a small London apartment, and both are said to be rented out.

Alastair Campbell, who was director of communications to Labour prime minister Tony Blair, said Johnson should not enjoy any more perquisites including a departing premier's right to nominate state honours.

He appears "determined to squat in a country home so he can have his oligarch funders round for fun and games, and resignation honours parlour games," Campbell tweeted. "Just go, crook."

Prominent Conservatives including former prime minister John Major also said it was dangerous politically to allow Johnson to cling on for so long.