Whitehall has blocked the release of a record number of historical documents, sparking criticism from transparency groups.
Government departments applied to stop 986 documents being released last year, an increase on the 460 in 2013.
The documents should have been released under the 30-year rule but the departments applied to block publication on grounds they could undermine foreign relations or defence and security.
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The papers in question are from 1986 and 1987 when Margaret Thatcher was prime minister and include papers on arms sales to India and Saudi Arabia, according to The Times.
The Advisory Council on National Records and Archives accused departments of “not giving enough thought” to the applications to block publication.
It said it had asked for a meeting with Whitehall officials and more than 20 attempts to block publication were rejected last year, as opposed to three in 2014.
The watchdog also said there was “a noticeable trend for departments to withdraw their applications when challenged” which implied the request should not have been put in originally.
Transparency International UK’s Robert Barrington said: “This report suggests there is still a culture of opacity within many government departments.
“A lack of disclosure can often lead to concerns that the government has something to hide and therefore transparency is the best measure to ensure public trust.”
Liberal Democrat leader Sir Vince Cable said the report was “an affront to our democratic ideals”.
“It is in everyone’s best interest to know what their government is doing,” he said.
A government spokesman said: “Last year 95% of government records that were transferred to the National Archives were made public.”