No10 declined on Tuesday to deny suggestions that the prime minister received a loan from the Conservative Party to cover the initial costs, before repaying the party.
But that claim appears to run contrary to what Mr Johnson’s then press secretary Allegra Stratton said last month when she denied any party funds were used for refurbishments.
As Mr Johnson faced mounting questions over the work, Labour deputy leader Angela Rayner urged Cabinet secretary Simon Case to expand his review to investigate the comments.
She urged him to probe “whether the former press secretary knowingly misled journalists and the public, or was misled herself by senior members of the Government who seem intent on a cover-up”.
The prime minister was facing continued questions of how the works were paid for, after former aide Dominic Cummings said Mr Johnson wanted donors to “secretly pay” for the work in an “unethical, foolish, possibly illegal” move.
The Tories declined to deny a suggestion, first reported by ITV, that the Conservative Campaign Headquarters paid the Cabinet Office to cover initial costs of the refurbishments, with Mr Johnson now repaying the party.
The prime minister’s official spokesperson said: “Any costs of the wider refurbishment in No10 have been met by the prime minister and he has acted in accordance with the appropriate codes of conduct and electoral law.”
He was pressed on a denial made by Ms Stratton in a Westminster briefing with journalists on 8 March.
“Conservative Party funds are not being used to pay for any refurbishment of the Downing Street estate,” she had said.
But asked about suggestions to the contrary on Tuesday, Mr Johnson’s spokesperson said: “I’ve seen the reports and the speculation on that, I’m not going to jump ahead of any potential declarations that need to be made.”
Mr Case, the head of the Civil Service, has been tasked with reviewing the refurbishment of the flat in No11.
In a letter to him, Ms Rayner said: “As a special adviser, Allegra Stratton is bound by the Civil Service Code, which sets out standards of integrity and honesty required from public officials.
“Therefore, I would urge you to build into your review an investigation into whether the former press secretary knowingly misled journalists and the public, or was misled herself by senior members of the government who seem intent on a cover-up.”
Ms Stratton, who moved roles this month after No10 scrapped plans to hold televised press briefings fronted by the former journalist, is yet to respond.
Labour has said that the “stench” surrounding the issue “will only grow” unless Mr Johnson publishes the long-delayed list of ministers’ interests.
Mr Johnson’s spokesperson said that list, last published in July, would not be updated until after No10 appoints a new independent adviser on ministerial standards.
Sir Alex Allan resigned from the role in November in response to Mr Johnson standing by Home Secretary Priti Patel despite an investigation finding her conduct “amounted to behaviour that can be described as bullying”.
“The declaration of interests that will be made available once we’ve appointed the replacement for Alex Allan, that work is in train,” the spokesperson said.
“One of the first things that person will then do is then look at the ministerial interests and then make sure they can be published in the normal manner.”
Mr Case has said there is a budget of up to £30,000 per year for prime ministers to renovate their Downing Street residency, with any costs beyond that met privately by those in office.
But last week the Daily Mail published details of an email from Tory peer Lord Brownlow in which he said he was making a £58,000 donation to the party “to cover the payments the party has already made on behalf of the soon-to-be-formed ‘Downing Street Trust”’.
Labour has called for a full investigation by the Electoral Commission, which said it is talking to the Conservative Party about whether the refurbishment spending falls within its remit.
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