The Conservative Party has been fined £17,800 over the redecoration of Boris Johnson’s Downing Street flat.

The Electoral Commission fined the party for “failing to accurately report a donation and keep a proper accounting record”.

The commission’s investigation found that decisions relating to the handling and recording of the donation reflected “serious failings in the party’s compliance systems”.

Louise Edwards, director of regulation at the Electoral Commission, said: “The party’s decisions and actions reflected serious failings in its compliance systems.

“As a large and well-resourced political party that employs compliance and finance experts, and that has substantial sums of money going through its accounts, the Conservative Party should have sufficiently robust systems in place to meet its legal reporting requirements.”

How much did Boris and Carrie Johnson’s Downing Street flat renovation cost?

A Tory donor provided more than £52,000 to cover some of the costs of Boris Johnson’s lavish renovations to his Downing Street residence, according to party accounts.

The refurbishments to the flat in No 11 sparked sustained scrutiny of Mr Johnson’s finances, with the works vastly exceeding the £30,000 annual limit afforded to the Prime Minister.

The National Wales:  The door of 11 Downing Street, London. Photo: PA. The door of 11 Downing Street, London. Photo: PA.

Published Conservative Party accounts said its central office provided a “bridging loan” of £52,802 to cover the works after being invoiced by the Cabinet Office in June last year.

The party was “reimbursed in full” by Lord Brownlow in October, before Mr Johnson “settled the costs” incurred by the Conservative peer in March.

Revealing the details on page 25 of the 26-page accounts, the Conservatives pointed to a review by the Prime Minister’s own ministerial standards adviser, Lord Geidt.

He found Mr Johnson acted “unwisely” in allowing the refurbishment to go ahead without “more rigorous regard for how this would be funded”, but did not breach the ministerial code.

The standards adviser said Mr Johnson had not been aware that Lord Brownlow had initially settled an invoice for the works.

A Cabinet Office report in July said more than £28,000 was spent on painting and sanding floorboards, coming close to the limit of public funding.

But additional invoices came in and in March the supplier – Soane Britain, which is owned by interior designer Lulu Lytle – refunded the Government, which then refunded the Tories, before Mr Johnson met “all final costs”, the annual report detailed.

Speaking earlier this year, a Conservative spokesman said: “As stated, the party provided a short-term bridging loan that was reimbursed to the party in full.”