The Marquess of Salisbury is a director of a trust that helps to bankroll the Conservative party from properties that it owns.

His involvement does not appear on any filings made by the Tories to the Electoral Commission, which monitors party funding. The disclosure comes amid pressure on the Tories from opposition parties and the electoral watchdog to reveal more details about their funding.

The party accepts money from a number of unknown or obscure organisations, trusts and companies — devices, it is claimed, that are used to avoid public scrutiny of donors.

David Cameron has also refused to reveal the identities of those who loaned the party money in the past, including one foreigner who is banned from making donations.

Salisbury was the party’s leader in the Lords between 1994 and 1998. He was sacked by William Hague, then the Tory leader, for negotiating a deal with Tony Blair to scrap all but 92 hereditary peers. Salisbury was given a life peerage but has been on a leave of absence since 2001 in protest at the threat of having to declare his financial interests.

It has now emerged that the marquess and his family are responsible for the Stalbury Trust, which has declared donations of £200,000 to the party since 2001. The identities of those behind the trust have, until now, remained hidden.

The stated purpose of the trust is to fund the “promotion of Conservative principles for the benefit of the Conservative cause or party”. Accounts show that throughout the 1990s it made donations to unspecified recipients of up to £100,000 a year, which means it could have given more than £1m to the Tories.

Ulric Barnett, a retired investment banker who is also a director of the trust, said yesterday: “It has investments which support the Conservative party. The funds go back a long way.” The other directors are Lord Cecil and the Earl of Verulam. Salisbury declined to comment this weekend.

Salisbury is also revealed as a key figure in another organisation that has been bankrolling the Tories. The United & Cecil, a dining club, raises money from its wealthy backers in parliament and the business world that is then handed to the Tories. It has given almost £150,000 over the past five years.

The club, which was set up by an ancestor of the marquess of Salisbury, meets eight times a year. It is headed by Tony Baldry, a controversial MP who was recently criticised for failing adequately to separate his public concerns from his private interests.

A member who was knighted by the Tories said: “At the beginning of a new administration they launch a voluntary appeal among members and the money is given to the party. There are usually a few big donations.”

The Conservatives are already under pressure to reveal the identities of those behind another secretive group — the Midlands Industrial Council.

The council consists of about 30 industrialists based in the Midlands and raises money for the party; it has donated almost £1m over the past three years. However, it has never published accounts nor divulged the names of its backers.

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