Survivors of the July 7th terrorist attacks in London and relatives of those killed are to take their calls for a public inquiry to the British Home Office.
A letter addressed to Home Secretary John Reid and calling for a wide-ranging inquiry will be handed in at the department.
The move by the 7/7 Inquiry Group comes a day after it was revealed that MI5 had come across ringleader Mohammed Sidique Khan and right-hand man Shehzad Tanweer while investigating another group of plotters.
The revelation during the fertiliser-bomb-plot trial at the Old Bailey prompted questions over the accuracy of some of the information families and survivors of the 7/7 attacks had been given.
Jacqui Putnam, a survivor of the Edgware bomb, said she had been told the bombers were acting alone but that what emerged from the fertiliser trial appeared to undermine that. "What else have we not been told?" she said.
Survivors and families said a public inquiry could help establish what steps, if any, could have been taken to prevent the 2005 attacks.
Mr Reid said on Monday he was "perfectly open to an inquiry" into the Security Service's handling of intelligence about Khan and Tanweer, but a public inquiry could not be held until after the trial of three people in connection with the July 7th attacks.
PA