The Cabinet Office Propriety and Ethics Team last month launched an investigation into allegations that the company which employs Philip May, the husband of the Prime Minister as an investment manager could have potentially made large sums of money from Brexit market movements caused by Theresa May’s decisions.

The complaint alleges a potential breach of the code of conduct for ministers which says: “Ministers must ensure that no conflict arise, or appears to arise, between their public duties and their private interests.”

 Sources say Sue Gray, director general of Propriety and Ethics at the Cabinet Office ordered an investigation into the allegations last month. Nothing more has been heard of this.

The central point of the complaint is that the Capital Group, a global investment company which manages $1.4 trillion of assets for corporations and high net worth individuals, could have had knowledge of market sensitive information that would have benefited their clients over Brexit. The situation would particularly apply to currency movements.

Philip May who works for the Capital Group, could, in theory as the PM’s husband, have had some prior knowledge of major political decisions by his wife.

He could also have recused himself from such decisions in the Capital group to prevent such a conflict. But the declaration of interests by Mrs May do not disclose his exact role and the preamble to the declaration says to disclose such details “would involve unjustifiable intrusion into the private affairs not only of Ministers, but of their close family.”

A Cabinet Office spokeswoman said today: “ We cannot and do not usually comment on private emails. We are also in a period of purdah so this could be a matter for Conservative Central Office”.

Mrs May has already faced some controversy over the way she had handled her financial affairs since she became Prime Minister.

Unlike David Cameron who sold all his shares to avoid any potential conflict of interest, Mrs May decided to keep her portfolio secret when she became Prime Minister and set up a blind trust- which means she should have no say in how it is invested.

This came under fire from opposition parties who said she should disclose it as part of government transparency but she refused. As a candidate for the leadership of the Tory Party she did disclose how much money she was receiving from dividends from shares – some £4914 which led to speculation the portfolio could be worth around £145,000.

Theresa May has had to disclose the role of her husband and make a more detailed declaration in the Ministers Lists of Interests than in her register of financial interests as an MP because the rules are stricter. Both registers should be read in conjunction as they do not duplicate information.

Nor is Mrs May a stranger to rows over ministerial interests. In 2010 there was a row between her and Michael Gove, then education secretary, over accusations that Michael Gove had failed to act to curb extremism in schools.

It was argued that this incident meant either or both parties were in breach of the section of the Ministerial Code which states: “the privacy of opinions expressed in Cabinet and Ministerial Committees, including in correspondence, should be maintained” .

The Cabinet Secretary was instructed to conduct an investigation into the dispute, and it was subsequently reported that the Education Secretary had apologised to the Prime Minister and the Home Secretary’s special adviser, Fiona Cunningham, had resigned after it was found she had been the source of a negative briefing against Mr Gove.

UPDATE:  “A Cabinet Office spokesman said: “The Prime Minister has declared in full her interests and the interests of her husband. There is no conflict of interest.”