The extent of the donations scandal afflicting Labour has widened after fresh allegations concerning Cabinet minister Alan Johnson emerged.

A newspaper claimed on Sunday the health secretary’s campaign team had accepted a proxy donation worth £3,334 during his unsuccessful 2007 bid to become the party’s deputy leader.

The claims come days after work and pensions secretary Peter Hain resigned to clear his name in light of a police investigation into donations received during his own deputy leader campaign.

According to the Sunday Mirror, Pakistani student Waseem Siddiqui, 50, had been asked by his Labour official brother to write a blank cheque.

The newspaper says Mr Siddiqui, who has lived in Croydon, south London, on a student visa for the last three years, has “no interest” in either Mr Johnson or the Labour party.

His brother, Ahmed Yar Mohammed, is the treasurer of Croydon central Labour party, the Sunday Mirror says.

Under electoral law, political donations cannot be made anonymously and must be declared within two months, a deadline the newspaper says Mr Johnson’s campaign team missed by four months.

The Electoral Commission, which referred undeclared donations to Mr Hain worth more than £100,000 to the Metropolitan police last week, is already investigating proxy donations to Labour from property developer David Abrahams.

Responding to the Sunday Mirror’s claims, Mr Johnson’s campaign team said: “We had no reason to believe the donation came from anyone other than [Mr Siddiqui].

“We checked he was a member of the Labour party and was on the Electoral Register and we registered the donation with the Labour party, the register of members’ interests and the Electoral Commission.”