A LETTER sent to Federal Attorney-General George Brandis by the Lindt Cafe gunman was missed by the federal siege review because of "human error", a Senate hearing was told.
The letter was missed because someone had failed to realise it was on the second page of a spreadsheet, department staff told the hearing.
"It was a human error essentially," deputy secretary Tony Sheehan told senators.
Senator Brandis originally said the letter had been included, but earlier this month Foreign Minister Julie Bishop told parliament the document had not been supplied because of an administrative error.
Monis and two hostages died as the 17-hour siege in Sydney was ended on December 17 last year.