The deletion of millions of government e-mails could harm the ability of key probes like the Hutton Inquiry, a senior MP has warned.
Mr Beith urged the information commissioner to look at the issue
Cabinet Office staff have been told to delete e-mails more than three months old - just days before new freedom of information laws come into force.
It was "too unlikely to have been a coincidence", said constitutional affairs committee chairman Alan Beith.
Tory leader Michael Howard has written to Tony Blair demanding an explanation.
But a Cabinet Office spokeswoman said the move was not about the new laws or "the destruction of important records".
"Paying to store outdated records which are no longer any use wastes taxpayers' money," she said.
But Mr Beith said: "It could quite clearly lead to the removal of information which is absolutely crucial in a range of events, whether you look at the current inquiry into David Blunkett or the Hutton Inquiry, where e-mails were so crucial in following the trail."
He argued that many things that were once said on the phone were now enclosed in emails - thus providing a written record.
E-mail records were therefore now crucial to finding out the reasons for "controversial decisions", he said.
"This is not supposed to be an inconvenient chore for departments. There is supposed to be a change in culture where it is recognised that the public is entitled to know all these things about the way in which the government makes its decisions."
THE NEW ACT
The public authority must say if it has information requested
If it does, applicants have the right to be told that information
All requests must be in writing
Authority must respond within 20 working days
Authorities have right to charge for providing information
The information commissioner should look how the "e-mail regime" can "support the freedom of information regime", he added.
The Cabinet Office's 2,000 civil servants have been told to print and file e-mails that should be disclosed, but there will be no supervision, according to reports.
The deleted e-mails will be stored on back-up systems which are beyond the reach of the Freedom of Information Act because of the cost of accessing them, the Times said.
In his letter to the prime minister, Mr Howard suggested the motive for the move was to "get round the law which you yourself passed".
"How hypocritical can you get? What is your government trying to hide?
"The public are entitled to a clear and simple explanation as to what is going on."
The Freedom of Information Act will cover England, Wales and Northern Ireland from next year. Similar measures are being brought in at the same time in Scotland.
It provides the public with a right of access to information held by about 100,000 public bodies, subject to various exemptions.
Its implementation will be monitored by the information commissioner.