Britain's Prime Minister Rishi Sunak is under investigation over whether he clearly declared his wife's shareholding in a company that stands to benefit from a recent budget.
The Parliament's Commissioner for Standards began the investigation over a "declaration of interest" on April 13, according to a list of open inquiries on its website on Monday.
The probe pertains to shares Akshata Murthy holds in childcare agency, Koru Kids, which is set to benefit from support for the childcare sector announced in March's budget.
Sunak did not mention Murthy's shares in the firm at a recent committee hearing.
The parliamentary rules demand that "members must always be open and frank in declaring any relevant interest in any proceeding of the House [of Commons] or its committees."
Last month, Chancellor of the Exchequer Jeremy Hunt announced a pilot of incentive payments for childminders joining the profession, which doubles if workers sign up through one of six agencies, including Koru Kids.
The investigation is an embarrassment for Sunak, who came into office in October promising to lead a government with integrity "at every level" as he sought to revive his party's fortunes ahead of a national election expected next year.
He has since received a police fine for not wearing a seatbelt on top of another for breaching lockdown rules when he was finance minister under former prime minister, Boris Johnson.
Sunak and Murthy are the richest ever occupants of 10 Downing Street. Murthy is the daughter of one of the founders of India's IT giant Infosys and owns about 0.9% of the company, worth nearly $600 million based on Monday's share price.
The couple had already faced criticism and public anger while Sunak was finance minister over Murthy's "non-domiciled" tax status. It meant she did not pay tax in Britain on her earnings abroad. Murthy finally gave up the status and said she would pay British tax on her global income.
The commissioner is responsible for the House of Commons code of conduct under which members of parliament must provide information about financial interests that might influence their work in parliament.
If the investigation finds a breach, the commissioner can require Sunak to apologize and set out steps to avoid any future errors, or refer him to a committee, which has the power to suspend or expel him from parliament.