British Prime Minister is facing calls to reveal details of her investments after it emerged that she has shares in a "blind trust", a newspaper here reported.
May had set up a blind trust when she became the PM, despite previously serving in the Cabinet for six years as Home Secretary, said the report in the Independent on Wednesday.
Downing Street insisted that May used what is a "well-established mechanism" when she set up the trust to manage her financial interests on becoming Prime Minister.
"I'm sure the Prime Minister has nothing to hide but the public has a legitimate interest in what companies she invested in and who runs the trust," Liberal Democrat leader Tim Farron was quoted in the newspaper as saying.
"Theresa May promised the most transparent government in the world. This is an early test to see if her deeds match her words," he said.
Shadow minister without portfolio Andrew Gwynne said: "If the Prime Minister has nothing to hide, then she needs to reveal immediately where she has existing financial interests."
The placing of shares in a blind trust means ministers have no knowledge of how their interests are being invested, to avoid accusations that their decision-making is unduly influenced.
But while ministers use the trusts to avoid conflicts of interest, six serving members of the government hold them. It also means they do not have to reveal their investments in full in the list of ministerial interests, said the report.
"Blind trusts are a well-established mechanism for protecting ministers in the handling of their interests, as they are not involved in any decisions on the management, acquisition or disposal of items in the trust. She set it up when she became Prime Minister," a Number 10 spokeswoman said.
The spokeswoman also said the Prime Minister did not require a blind trust while she was Home Secretary, adding: "The Prime Minister has a far wider set of public duties than the Home Secretary."
The arrangement has proved controversial in the past. Former Prime Minister Tony Blair attracted criticism in 2002 after it emerged his wife Cherie had used money from his blind trust to buy two flats in Bristol.