Labour is demanding investigations into fresh standards allegations against the Prime Minister and Commons Leader Jacob Rees-Mogg as sleaze claims continue to ple pressure on the UK Government.

The opposition party at Westminster has said that new information from American entrepreneur Jennifer Arcuri about her relationship with Boris Johnson while he was mayor of London should be investigated by the Independent Office for Police Conduct (IOPC).

Mr Johnson avoided a criminal investigation earlier this year into his conduct with the businesswoman after the police watchdog found no evidence he had influenced the payment of thousands of pounds of public money to Ms Arcuri or secured her participation in foreign trade trips he led.

But after the Observer published Ms Arcuri’s diary notes from the time of their alleged dealings, deputy Labour leader Angela Rayner said the IOPC should “look again” at its decision to rule out a formal investigation.

According to the newspaper, one handwritten entry recalls that Mr Johnson asked how he could be the “throttle” in her career while he was in City Hall.

As well as having business links, Ms Arcuri has previously claimed that she and Mr Johnson had a four-year romantic relationship when he was mayor.

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Ms Rayner has written to the Greater London Authority’s monitoring officer, Emma Strain, to request that she refer Ms Arcuri’s remarks to the IOPC.

In her letter, she said the reports were “deeply worrying” and “emblematic” of Mr Johnson’s approach to political leadership, which she claimed had “no regard for decency or public interest, only self-interest”.

Labour also wants Mr Rees-Mogg investigated by Commons standards commissioner Kathryn Stone over claims in the Mail On Sunday that the prominent Conservative MP failed to declare director’s loans from his company Saliston Limited between 2018 and 2020 Shadow Commons leader Thangam Debbonaire said: “This would appear to be yet another egregious breach of the rules.

“A Cabinet minister failing to declare millions of pounds of additional income is unacceptable.”

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The allegations come after the Department for Transport (DfT) hit back at claims in the Sunday Times that Grant Shapps, a keen pilot, is using a lobbying body to protect airfields from development.

The Transport Secretary – who is said to own a £100,000 aeroplane – “set-up and diverted public money” to a new team within the Civil Aviation Authority which is designed to lobby against planning developments, including housing projects, that infringe on airstrips, according to the reports.

But DfT officials said the Airfield Advisory Team was not a lobbying body and instead provided “support to general aviation on a range of matters affecting their operations”.