Prime Minister Gordon Brown will on Wednesday outline the security threats facing Britain and his government's plans to tackle them.

Brown will identify pandemics, climate change, failed states and access to energy supplies as potential threats as he unveils a national security strategy, aides said on Tuesday.

Britain is also at risk from global terrorism, nuclear weapons falling into the wrong hands and regional tensions in areas such as Afghanistan or the Middle East, the aides added.

The strategy will set out how spy agencies, government departments, the police, the military and global institutions are collaborating to protect Britain, as well as detailing what else is needed to support them.

"We face a new terrorism threat of a different scale and nature," Brown's spokesman said.

"We continue to face the threat of nuclear weapons but we face now new forms of attack such as electronic attacks and increasing risks such as pandemics and also a deeper understanding of how issues like climate change and energy demand affect our national security," he added.

Brown will set out the security strategy in a statement to parliament at 12:30 p.m.

The strategy, intended to be published annually to update the country on the nature of the risks, will also highlight the growing complexity of the terrorism threat facing Britain.

"Now we face a loose affiliation of terrorist groups and networks spanning the globe and we also see how failed states such as Afghanistan and regional tensions such as those in the Middle East affect our national security," the spokesman said.

Britain has been the target of Islamist extremists in recent years while tensions with Russia have raised concerns over the security of energy supplies.

Brown set up a National Security Committee in July last year, with a remit to discuss all issues relating to defence and counterterrorism and to oversee the national security strategy.