Survivors and families of victims of the 2005 London suicide bombings that killed 52 people are pressing Britain's Home Office to authorize a new and independent probe of the blasts.

The request was made in a letter Tuesday to Home Secretary John Reid, following a trial in which five suspects planning to explode fertilizer bombs in southern England were sentenced to life in prison.

In that trial, which ended Monday, evidence showed agents photographed and recorded two bombers who later blew themselves up in the London subway, conferring with fertilizer bomb plotters 17 months before the transit bombings occurred.

The interior minister at the time, Charles Clarke, said in 2005 that none of the suicide bombers had been known to police.

There has been no public response to the letter handed to the Home Secretary.

Police have acknowledged the link between the two sets of bombers. But authorities have argued that Muhammad Sidique Khan, who was sentenced Monday, was not involved in terrorist activity when the photos were taken three years ago.

Some information for this report was provided by AFP, AP and Reuters.