LONDON - Prime Minister Gordon Brown called on Sunday for the immediate release of five British hostages held in Iraq and said their detention would not sway Britain's approach to the country.

His made the appeal days after the captors released a video of one of the men and said they would kill them all unless Britain withdrew all its troops from the country.

"The taking of hostages is completely unjustified, wholly unacceptable and we are making it clear they will not change our policy in any way," Brown said.

"We will do everything in our power to secure our objective, which is the immediate release of the hostages."

The four security guards and one computer expert were taken prisoner in May by abductors dressed as Iraqi police in a finance ministry building in Baghdad.

"I want the hostage takers to accept their responsibility, to understand the consequences of what they are doing, to make possible the immediate release of the hostages, to allow them to come home at the earliest opportunity," Brown said.