Mistakes that led to the loss of 25 million child benefit records can not be blamed on a single government official, a report is expected to say.
The loss of two discs containing the personal details 25 million people was "entirely avoidable," a report says.
The Poynter report could cast doubt on government claims one junior member of staff was responsible for the breach.
The Poynter report does not blame individual officials but points to serious structural failings at HM Revenue and Customs offices.
It will highlight "cultural failures" at HM Revenue and Customs (HMRC) and say practices were "far from what they should have been," sources say.
Chancellor Alistair Darling told MPs action was already being taken to improve data security.
A Cabinet Office report on government data will also be published later.
A separate report by the Independent Police Complaints Commission will be published later.
It will look at the broader issue of how government departments handle personal data.
It is expected to back many of the changes that have been brought in following a string of missing data scandals - including giving the Information Commissioner powers to carry out spot checks on departments and agencies.
'Junior official'
The Poynter report will focus on the loss of the HMRC discs in October last year.
The child benefit records - including personal details of 25 million people - were posted from an HMRC office in the North East of England to the National Audit Office on two discs.
When the discs failed to arrive at the NAO's offices in London, another copy was sent that did reach its destination.
But police were unable to locate the missing information, raising fears that it could be exploited by identity thieves.
Chancellor Alistair Darling briefed MPs on the missing data in November, insisting a "junior official" had been responsible for posting the information "contrary to all HMRC standing procedures".
Prime Minister Gordon Brown - who set up HMRC when he was Chancellor - expressed "regret" at the loss of the data but also stressed that it was a result of rules not being followed rather than "systemic" failures.
But Wednesday's report, by management consultant Keiran Poynter, could cast doubt on that version of events and highlight wider "cultural" problems at the department.
In a third report, also to be published later, the Independent Police Complaints Commission (IPCC) will disclose its own findings on the HMRC data breach.
The Ministry of Defence will also issue a report on how a laptop containing details of 600,000 potential armed forces recruits was lost - which is said to highlight a slack culture among staff.
