The Tories have branded the government "hypocritical" over reports officials will delete millions of e-mails before new data laws take effect on 1 January.
Mr Howard asked what the government was 'trying to hide'
The Cabinet Office has ruled e-mails older than three months must be wiped from Monday.
Conservative leader Michael Howard has written to Tony Blair demanding an explanation for the move.
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"Paying to store outdated records which are no longer any use wastes taxpayers' money," she said.
According to a report in the Times, 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 Cabinet Office's 2,000 civil servants have been told to print and file
emails that should be disclosed, but there will be no supervision, the paper said.
But a Cabinet Office official told the Times: "We are not going to get some 25-year-old graduate deleting the advice which the Attorney-General gave to the Government about going to war with Iraq."
However, Mr Howard questioned the motives for the e-mail deletion.
In his letter to Mr Blair he wrote: "There are reports that your Government is engaged on a massive e-mail destruction binge in order 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.
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 Act 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.
The assistant information commissioner, Phil Boyd, told the Times deletion of Cabinet Office e-mails could see important files lost.
Meanwhile, the Department for Constitutional Affairs told the paper: "No Government Departments have been told to destroy records in order to prevent their release under the FoI Act, and such a policy would run totally contrary to the Government's intention to increase openness.
"Departments regularly destroy records as part of proper records management policies. Paying to store outdated records which are no longer of any use, and which are not historically valuable, wastes taxpayers' money."