Police have hacked into computers at Downing Street as they search for evidence in the cash-for-honours scandal, newspaper reports claim.

Detectives at Scotland Yard allegedly hired computer experts to obtain private information, including emails, letters and other electronic data, according to the Sunday Telegraph.

It is also understood that officers contacted the government’s internet service provider to access further email records.

The newspaper report states that the Metropolitan Police became suspicious that officials at Number 10 were withholding information, after asking for all emails and material related to the peerage system and receiving a “very slim” file of documents.

The paper claims that the police obtained high level authorisation to access the computer systems, possibly from John Yates, the Met’s assistant commissioner, who is leading the investigation.

A Westminster source told the newspaper that computer experts used forensic software to scan the machines for files related to the allegations.

“Quite clearly, in the past few days, the police have found something quite significant, possibly a file dump of some kind,” they said. “They have been using specific software of the type they use in complex fraud cases.”

The forensic search came shortly before the arrest of Ruth Turner, one of Prime Minister Tony Blair’s top advisers, on suspicion of perverting the course of justice on Friday.

Police are permitted to intercept electronic communications without notifying the subject of the investigation using laws under the Regulation of Investigatory Powers Act 2000.