An inquiry has been launched into the charity set up in honour of fundraiser and Army veteran Capt Sir Tom Moore.
The Charity Commission has concerns about The Captain Tom Foundation's management and family independence related to trademark issues.
The veteran, who died last year aged 100, raised millions for NHS Charities Together by walking laps of his garden. This money is not part of the inquiry.
The Foundation said it would "work closely with the commission".
Capt Sir Tom, who was born in Keighley in West Yorkshire, gained international fame when he carried out the fundraising walk at his home in Marston Moretaine, Bedfordshire, when Covid restrictions were first introduced in 2020.
The £33m raised, £38.9m including gift aid, was managed and distributed by NHS Charities Together before the JustGiving account was closed down.
After he became a well-known figure, his family set up a separate charity in his name called The Captain Tom Foundation, which aims to support and "empower" older people through fundraising and awareness campaigns.
The money raised by Capt Sir Tom was separate from the formation of the charity and is not part of the investigation.
In March 2022, the publication of the first annual accounts of the foundation showed it had incurred £240,000 in costs and given £160,000 to good causes.
The commission said it became concerned about arrangements between the charity and a company linked to Sir Tom's daughter, Hannah Ingram-Moore, and her husband Colin, as well as the trustees' decision-making and how the charity was governed.
The issues revolve around a "failure to consider intellectual property and trademark issues", including the trademarking of variations of the name "Captain Tom" by a company controlled by Ms Ingram-Moore and Mr Ingram-Moore.
This could have generated "significant profit" for the company, the commission added.
Helen Stephenson, chief executive of the Charity Commission, said the watchdog's "concerns have mounted" over the charity.
"We consider it in the public interest to examine them through a formal investigation, which gives us access to the full range of our protective and enforcement powers," she said.
Earlier this year, the Commission but said it was later "satisfied" that these specific payments were a reasonable reimbursement for expenses incurred by the companies in the formation of the charity.
It added it was also satisfied that the payments were "adequately identified and managed".
Stephen Jones, chairman of the board of trustees of The Captain Tom Foundation, said: "We will of course work closely with the commission in its inquiry."
He said the commission was aware of where the image and intellectual property rights were held when the charity was set up.
Jack Gilbert, who became chief executive of the charity at the beginning of the month, said he would "ensure that in all respects, including governance and finance, the foundation conforms to best practice".
A statement from the Ingram-Moore family said the company controlled by Ms Ingram-Moore and Mr Ingram-Moore "made its application for various trademarks in April 2020 prior to the formation of The Captain Tom Foundation", which was in May 2020.
"Neither Hannah nor Colin Ingram-Moore were trustee directors of The Captain Tom Foundation upon its formation," the statement added.
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