Hilary Benn rejected a £5,000 cheque for his deputy leadership campaign after one of his supporters discovered that the donor was a middleman for David Abrahams, the wealthy property developer.

Baroness Jay of Paddington, a supporter of Mr Benn in the deputy leadership race, is believed to have made the link after coming across Janet Kidd at a meeting of Labour’s 1,000 Club, the network of donors who contribute at least £1,000 a year.

The Labour peer told Mr Benn, who then rejected the donation, believing that the offer was improper.

The revelation puts pressure on Harriet Harman, who insists that she was unaware that Ms Kidd was donating to her deputy leadership campaign on behalf of Mr Abrahams. Subsequently, Mr Abrahams sent a cheque in his own name to Mr Benn’s campaign, which was accepted and registered with the Electoral Commission.

Mr Benn’s spokesman said: “During the deputy leadership contest, Hilary Benn’s campaign was sent a cheque by Janet Kidd for £5,000. [Lady] Margaret Jay, who was supporting the campaign, made us aware that this donation was on behalf of Mr David Abrahams. We didn’t accept it because we felt that if Mr Abrahams wanted to make a donation he could do so in his own name. We returned the cheque. Subsequently, Mr Abrahams made a donation of £5,000 to the campaign, which we accepted and reported to the Electoral Commission as required. Hilary Benn was completely unaware that Mr Abrahams was making donations to the Labour Party nationally via others.”

Membership of Labour’s 1,000 Club is a secret since only donations over £5,000 must be entered in the Electoral Commission’s public register. There are approximately 250 members, and the donors provide more than £300,000 a year to Labour.

The organisation was set up for so-called “Labour luvvies” by Ken Follett, the millionaire author, while Neil Kin-nock was leader. The idea was for wealthy party members, each donating at least £1,000 a year, to be able to mix with senior politicians. Lady Jay later took over the running of the club.

Ms Harman became the surprise victor in the race to succeed John Prescott, beating Alan Johnson by less than one percentage point in a campaign in which she picked up votes by brandishing her left-wing credentials.

Following her victory, Gordon Brown moved quickly to limit her influence as Labour’s new deputy leader, announcing that she would have a party role rather than a top government job, and would not succeed Mr Prescott as Deputy Prime Minister.

Mr Benn came fourth overall, principally because of lack of support among MPs and MEPs.

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