Prime Minister Rishi Sunak is being investigated by Parliament’s standards watchdog over a possible failure to declare an interest.
Mr Sunak is being investigated over whether a declaration of interest was “open and frank”, under rules set out by the commissioner for standards.
The BBC understands the probe relates to a childcare firm his wife has shares in.
The commissioner decides whether an MP has broken rules after an inquiry.
A Downing Street spokesperson said: “We are happy to assist the commissioner to clarify how this has been transparently declared as a ministerial interest.”
Last month, Mr Sunak faced questions over shares his wife, Akshata Murty, holds in Koru Kids, a childcare agency that could benefit from a new policy unveiled in the spring Budget.
Chancellor Jeremy Hunt announced a pilot of payments for new childminders, with more for those who sign up through agencies.
Ms Murty was listed as a shareholder in one of those agencies, Koru Kids, as recently as 6 March.
Mr Sunak did not mention Ms Murty’s links to Koru Kids when he was questioned by MPs over the childcare policy at a parliamentary committee hearing on 28 March.
Labour MP Catherine McKinnell asked Mr Sunak whether he had any interest to declare, and in reply he said: “No, all my disclosures are declared in the normal way.”
In a letter to the committee, sent a few days after the hearing, Mr Sunak said his wife’s interest was declared to the Cabinet Office and that an updated statement of ministers’ interests would be due out shortly.
In his letter, Mr Sunak said the the list of ministerial interests “ensures steps are taken to avoid or mitigate any potential conflict of interest”.
The list of ministerial interests is separate to the register of interests for MPs, which says members “must always consider whether they have a conflict of interest”.