The property is owned by two companies controlled by Mr Robinson, which have not been registered in the Commons Register of Members' Interests.
Francis Maude, the Shadow Chancellor, has written to Sir Gordon Downey to ask for an investigation. His letter, to be delivered today, could spark the fourth investigation into Mr Robinson's affairs since he took office in May last year.
According to company records held in Siena, Italy, Mr Robinson bought the property in 1992. It consists of his holiday home, Villa Mucchio, visited for the last two summers by the Prime Minister, Tony Blair, and his family, a disused monastery which is being renovated and about 140 acres of farmland.
Sir Gordon, the Parliamentary Commissioner for Standards, has already completed an investigation into Mr Robinson's involvement with an offshore trust and with shares in Coventry City Football Club. He told Mr Robinson that his interest would have been better registered. He is still looking into two more claims that Mr Robinson failed to declare directorships.
Mr Maude's letter questions whether the Paymaster General has broken parliamentary rules by failing to declare relevant pecuniary interests.
Last night Mr Robinson said: "In response to a letter from Nigel Evans MP last August Sir Gordon Downey considered the issue of declaration of Villa Mucchio and Borgo Mucchio. He concluded that there was no breach of the rules relating to registration."
Storm over villa, page 3Reuse content