The Charity Commission is writing to four charities that appeared among more than 5,000 signatories of a letter to The Daily Telegraph newspaper in support of the Conservative Party, asking that they "remedy the situation swiftly".
Yesterday, the Telegraph published a letter that said the government "has been genuinely committed to making sure Britain is open for business", and saying: "We would like to see David Cameron and George Osborne given the chance to finish what they have started. A change now would be far too risky and would undo all the good work of the last five years."
Among the 5,025 signatories, whose names had been collected by the Conservative Party and then submitted to the Telegraph, are Keith Dewhurst, chair of Cardiff-based Diverse Cymru, William Morrison, centre manager and chair of the East Doncaster Development Trust, Adebimpe Oputa, project manager at the supported housing charity Marsha Phoenix Memorial Trust, and Uldis Revelins, chair of the Latvian Welfare Trust.
A spokesman for the commission said: "Signing a letter in support of a political party is not a legitimate activity for a charity. We will be writing to all four charities to establish the facts and expect them to remedy the situation swiftly if they have not done so already. The commission will decide what further action, if any, is necessary once the charities have responded."
The spokesman said the commission had already been made aware that Diverse Cymru and Marsha Phoenix had publicly asked for their names to be removed from the list, and said that this was "the right course of action".
Rebecca Long, director of Marsha Phoenix, said: "The named signatory is an employee of the trust who has confirmed she has not been approached to be signatory to such a letter as a small business owner. We believe our and her inclusion on this list is some sort of error."
She said the charity had contacted the newspaper and the party to ask for its name to be removed.
A statement posted on the website of Diverse Cymru yesterday said that although Dewhurst, who is standing as the Conservative parliamentary candidate for the Cynon Valley constituency, was a Conservative member and campaigner, this was separate to his role with the charity.
The statement said: "We believe we were included in error and have contacted the Conservative Party to remove our name from this list immediately."
A spokesman for the charity said it was yet to receive a response.
Morrison said he had not been aware when lending his support to the letter that the charity would be named, and said he would withdraw his name if required. He said that the charity would endorse anything supporting small businesses, but said: "It’s the principle we support, not the party. We’ve got to take a neutral stance."
It was not possible to contact Revelins or the Latvian Welfare Trust.
The letter has also been criticised for listing several individuals more than once and for containing several names of people who are also candidates in the general election, such as Dewhurst.
A spokesman for the Conservative Party said: "Representatives from more than 5,000 organisations signed up to this letter supporting the Conservative Party. Everyone whose name was published actively signed up to the letter on the Conservative Party's website."