Public bodies should be able to refuse Freedom of Information (FOI) requests on the basis it would take them too long to censor material, the MPs' expenses watchdog has said.
The Independent Parliamentary Standards Authority (Ipsa) has suggested the move to the Government's controversial commission reviewing the Freedom of Information Act.
Under existing rules, Whitehall departments can turn down FOI requests if they would cost more than £600 to answer, while for other public bodies the limit is £450.
But officials can only estimate the costs of determining whether material is held, retrieving it and extracting what has been asked for.
FOI supporters fear that including "redaction" costs - possibly meaning lengthy correspondence with individuals to assess what should be censored - could allow public bodies to refuse a swathe of legitimate requests.
The House of Commons could potentially have used such a limit to hinder disclosure of MPs' expenses in the past.
Ipsa is currently considering how to publish all receipts supporting MPs's claims in future, after a landmark ruling by the Court of Appeal found they provided more information than could be obtained from a list of individual transactions.
At a meeting with commission head Lord Burns last month, the watchdog's chairman Sir Ian Kennedy said it was looking at whether "sensitive information" could be "redacted at the same stage as the request is validated, rather than reactively once the information had been requested".
But he argued that the "back catalogue" of around a million receipts going back to 2010 would prove more difficult and expensive.
"Sir Ian explained that the Act as a whole did not impose significant burdens on Ipsa, but that the redaction of information in light of the Court of Appeal case was in itself burdensome," minutes of the meeting said.
"Sir Ian felt that redaction should be included as one of the activities that can be counted in assessing whether a request exceeds the cost limit, particularly where, for example, the Data Protection Act 1998 required it."