Boris Johnson has been accused of breaching the ministerial code after it was reported that he used a private jet paid for by taxpayers to campaign in the Hartlepool by-election.
Mr Johnson flew from the Stansted to Teeside on April l as he visited Middlesbrough on government business to promote his minimum wage policy, but he then travelled to Hartlepool to campaign, The Times reported.
The Prime Minister accompanied Jill Mortimer, the Conservative candidate, on a visit to Hart Biologicals before joining local party members to knock on doors in the constituency. Mr Johnson flew back to London that evening.
The Tories won the Hartlepool by-election for the first time in their history.
The Electoral Commission dictates that spending on transport costs at by-elections must be declared. The ministerial code states: “Where a visit is a mix of political and official engagements, it is important that the department and the party each meet a proper proportion of the actual cost.”
On Monday night the Conservative party admitted that the Prime Minister’s flights had been paid for by the taxpayer but insisted that Mr Johnson had only used the aircraft to carry out official government business during his visit to Middlesbrough.
Labour has called for an investigation and accused the Prime Minister of breaching the ministerial code, and possibly breaking the law.
In a letter to Lord Geidt, the PM’s adviser, Angela Rayner, Labour’s deputy leader, said: “False election returns or the non-declaration of election spending is a criminal offence.”
Candidates are only permitted by law to spend £100,000 on by-election campaigns. According to The Times, the Conservatives’ spending return for the campaign was £87,000 and the flights were not declared.
A No 10 spokesman said: “All relevant costs have been correctly accounted for and appropriately proportioned. At all times government rules and electoral requirements were followed.”
The Prime Minister was in July cleared of breaking the ministerial code after he went on holiday to Mustique and stayed in a villa paid for by David Ross, a wealthy Tory donor.
Mr Johnson was also being investigated by the Electoral Commission over the costs of renovating his flat in Downing Street.
No 10 has always maintained that an estimated £58,000 refurbishment of the flat above 11 Downing Street that Mr Johnson shares with his wife, Carrie, was paid for personally by the Prime Minister.
Mr Johnson was in May cleared of any ministerial code breach over the refurbishment of his Downing Street flat.