The Conservatives continue to lay the blame for the data security breach on Gordon Brown, arguing there are systemic failings in Her Majesty's Revenue and Customs (HMRC).
The government's version of the events that led to the loss of 25 million people's personal details, including bank accounts and addresses, has been contradicted by fresh claims from the Tories.
They claim to have seen emails showing senior officials at HMRC authorised the complete transfer of data to the National Audit Office (NAO), reasoning it would be too expensive to remove sensitive details.
The NAO reportedly told HMRC it did not need the full data records, including bank details and addresses.
Edward Leigh, the Conservative chair of the public accounts committee, said the way HMRC handled data prioritised costs over security.
He told Channel 4 News: "I think it's quite wrong - indeed outrageous - to pass the buck down to some poor official who's now been locked away in a hotel in County Durham.
"This was systemic failure going right up the Inland Revenue and questions must be asked; answers must be given."
In a statement to MPs on Tuesday, chancellor Alistair Darling said the information should never have been sent to NAO in the first place. The government has blamed an unnamed junior official at HMRC for sending the discs through unregistered TNT post.
Sir John Bourne, head of the NAO, reportedly has emails proving senior officials were aware of the massive data transfer.
Shadow chancellor George Osborne said last night: "These startling revelations from the NAO call into question the entire defence mounted by the prime minister of this catastrophic failure in his government.
"This was a systemic failure not individual error by a junior official".
In prime minister's questions yesterday David Cameron said job cuts and the merger between Customs and the Inland Revenue had created systemic problems in the new department.
The prime minister yesterday apologised unreservedly for the security failing and said no child benefit claimant would be left out of pocket.
Mr Brown has also ordered the cabinet secretary, Sir Gus O'Donnell, to carry out security checks on all government departments.
However, Mr Brown has refused to accept arguments this week's security blunder undermines the government's credibility to run a national ID database.