Last night the Countryside Alliance said it had sold the names of 30,000 supporters to the Tories through an agency for about pounds 1,500, but insisted the deal was above board.
In a letter to the countryside campaigners, Mr Hague admitted the Tories had lost power because "we lost touch with the people we always claimed to represent".
Labour MPs were mostly from urban areas and cared little about countryside issues, Mr Hague wrote. In particular, they wanted to ban hunting with hounds and bring in a "Right to Roam" law.
He then added: "Providing a voice for the countryside costs money ... I would be very grateful if you would be kind enough to complete the enclosed form and return it with a donation in the Freepost envelope provided."
Last night the Assistant Data Protection Registrar, David Smith, said the Countryside Alliance did not appear to have registered itself with the body.
"In view of the interest and the public concern about this matter, we will certainly investigate. If an organisation is holding personal data on computer and is disclosing it to other organisers they ought to be registered with us," he said.
He also suggested a letter sent out to members by the British Field Sports Society asking if they would allow their names to be disclosed was not adequate.
The letter was not sent by the Countryside Alliance and only mentioned passing on names to commercial and charitable bodies, not political parties.
Janet George, chief press officer for the Countryside Alliance, said the revelation was a "desperate" attempt by the League Against Cruel Sports to undermine the campaign.
"All new members get a letter explaining that we do from time to time sell or loan our mailing list," she said.Reuse content