Brown said the incidents were "designed to cause maximum carnage."
He spoke to British television ahead of the second anniversary of the July 7, 2005, London transport system bombings that killed 52 people.
Earlier, Australian police said they questioned five doctors of Indian background and raided two hospitals in connection with last week's failed bombings in Britain.
"There are now a number of people now being interviewed as part of this investigation," Australian Federal Police Commissioner Mick Keelty told reporters today in Canberra. "It does not mean they are all suspects, but it is quite a complex investigation, and the links to the U.K. are becoming more concrete."
"There is nothing to suggest those who have been spoken to in Australia are necessarily guilty of an offense, but we are trying to establish what the linkages are and whether there is any criminal aspect to those linkages," he added. "In any event the work that we are doing here will be in support of the investigation in the United Kingdom"
Police in western Australia arrested an Indian doctor on July 2 after five foreign-born doctors were detained in Britain following the attempted attacks. Reports say two doctors detained in Britain applied for jobs in western Australia in the past two years.
(AP, AFP, dpa)