Labour is calling for an investigation into an alleged arrangement by which Boris Johnson used a relative to act as a guarantor for an £800,000 credit facility when he was prime minister. The party has written to the parliamentary standards commissioner after the Sunday Times reported Canadian businessman Sam Blyth, a distant cousin, had agreed to act as a guarantor for a credit facility for Johnson. Blyth is a friend of Stanley Johnson, Boris’s father. Their mothers are believed to be cousins. The 67-year-old was considered for the position of chief executive of the British Council, the body that represents the UK’s international cultural relations and educational opportunities, but the body decided against hiring him. The Sunday Times said that Johnson needed the financial help despite earning £164,000-a-year in Downing Street. An anonymous source said Johnson was on the verge of “going broke”, and had lost substantial earnings, including his column in the Daily Telegraph, when he became prime minister. A spokesperson for Johnson rejected any suggestion that a conflict of interest or a breach of the MPs’ code of conduct existed, adding that he made all the “necessary declarations he was required to make”. The Labour party’s chair, Anneliese Dodds, has written to the standards commissioner, Daniel Greenberg, saying there should be an urgent investigation. She referenced the MPs’ code of conduct, which says “holders of public office should not place themselves under any financial or other obligation to outside individuals or organisations that might influence them in the performance of their official duties”. She added that Johnson “may have breached this section by entering into an arrangement whereby he was dependent on the generosity of an individual who was, I understand, at the time standing to be chief executive of the British Council”. She added: “I’m concerned that, without adequate transparency over this arrangement, it may give the impression that this was a quid pro quo arrangement, something which would fundamentally damage faith in our democratic process.” She also said that the alleged arrangement was not properly declared. The revelation came as senior Tory backbencher David Davis used an article in the Independent to warn that allies of Johnson calling for his return were damaging the party. The former Brexit secretary, who called on Johnson to quit as prime minister last January, said: “Boris is not going to be the electoral asset that his acolytes claim. The continual drumbeat calling for his return is certainly going to fail, but in the process it is corroding the party’s chances at the next election.” A spokesperson for the former prime minister said: “This is nonsense. There is no conflict of interest or breach of the MPs’ code of conduct. There was never any loan made by Sam Blyth. “Johnson neither knew about nor in any way assisted Blyth in any application for any public position. “Johnson made all the necessary declarations he was required to make, for example, in the register of ministers’ interests. “At all times he acted on the instructions of officials, the cabinet secretary and the independent adviser on ministerial interests, as the Cabinet Office has confirmed.”