Prime Minister Tony Abbott said the Sydney Siege wouldn’t have been stopped had a letter from Man Haron Monis to the Attorney-General’s Department resulted in action.

The letter is at the heart of an attack from the opposition during Wednesday’s Question Time calling for the government to explain why it withheld the letter from an inquiry into the siege.

A Senate hearing on Tuesday night was told the Department of Prime Minister and Cabinet informed their colleagues at the Attorney-General’s department it hadn’t received the October 2014 letter on June 1, but the error wasn’t made public in parliament for three days, AAP reported.

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Man Haron Monis was known to anti-terror forces prior to the Sydney siege.

The letter from Monis asked Mr Brandis whether it was legal to contact the heads of Islamic State, and Attoney-General’s Department deputy secretary Tony Sheehan said the letter wasn’t disclosed because it was hidden on the second tab of a spreadsheet.

Mr Abbott told parliament that acknowledging the letter in 2014 prior to the fatal siege wouldn’t have stopped it occurring.

“Any proposition that they (the Opposition) might be advancing implicitly, if not explicitly, that somehow more attention to this letter would have prevented the Martin Place atrocity is simply fanciful,” he said.

“The secretary of my department has said that the provision of the letter in question to the inquiry would have made no difference to its findings.”

“I can also confirm that the Director-General of ASIO has said publicly that the letter in question was handled perfectly appropriately by the Attorney-General,” he said.

A cover-up of a cover-up

Tanya Plibersek was on the Getty

The Opposition called on the government to explain why it took days to correct the record. “This is a cover-up of a cover-up,” opposition foreign affairs spokeswoman Tanya Plibersek said.

Ms Bishop said she was told about the error after question time began, and didn’t have a chance to correct the record earlier than that because she was in France.

“Question time starts at 2. 2:43. Catherine Jones sent an email to the committee at 2:55pm,” she said.

“After question time, that is 14 minutes later, at 3:09pm, I corrected the record. I had no earlier opportunity to correct the record as I was in France until 4 June.”

On Wednesday during Question Time the Opposition launched a relentless attack on the government over the withheld letter, which ended with failed attempts to censure Ms Bishop, Mr Abbott and Mr Brandis over claims they misled parliament.

The government turned the tables on its attackers though, and used the parliament to silence the MP spearheading the assault, Tanya Plibersek, with a ruling she no longer be heard.