Anti-Bush protester Anna White, lays a red rose and a banner outside the White House in Washington, yesterday. - Reuters

WASHINGTON (Reuters):

President George W. Bush signed a law yesterday authorising tough interrogation and prosecution of terrorism suspects and took an indirect, election-year swipe at Democrats who opposed the legislation.

Bush, trying to help Republicans maintain control of the United States Congress by emphasising national security, called the Military Commissions Act of 2006 "one of the most important pieces of legislation in the war on terror."

Human rights groups charge that the measure would allow harsh techniques bordering on torture, such as sleep deprivation and induced hypothermia.

In a White House East Room ceremony, Bush praised members of Congress who approved the law over the opposition of the Democratic leadership in both the Senate and House of Representatives.

"Every member of the Congress who voted for this bill has helped our nation rise to the task that history has given us. Some voted to support this bill even when a majority of their party voted the other way," Bush said.

Much of the new law, which critics say still does not protect detainees' rights and predict will face legal challenge, was negotiated in September after senior Republicans rebelled against Bush's plan.