ARTICLE AD BOX
The Conservative Party has been fined £17,800 for "failing to accurately report a donation" that paid for the refurbishment of the PM's flat.
The Electoral Commission also said the party failed to "keep a proper accounting record" around the donation.
Over £52,000 was given to the party by Lord Brownlow for the work, initially paid for by the Cabinet Office.
A Tory spokesman said the party was considering whether to appeal and would make a decision within 28 days.
A row erupted earlier this year over how the refurbishment of the flat Boris Johnson shares with his wife, Carrie, above No 11 Downing Street was paid for.
The prime minister receives an annual public grant of £30,000 to spend on his living quarters. But there had been speculation the final bill came to as much as £200,000.
Mr Johnson's former chief adviser Dominic Cummings claimed the PM had planned to solve this shortfall by having donors "secretly pay" for the work.
But the prime minister insisted he "covered the costs".
The PM's adviser on standards, Lord Geidt, said a Tory donor had paid an invoice for some of the costs and that Mr Johnson had acted "unwisely" by not being more "rigorous" in finding out who paid.
But he cleared Mr Johnson of breaking ministerial conduct rules.