Robinson, a former assistant attorney-general, has found himself among the Americans who have been questioned and searched because they were though to be on the list.

He said he was routinely delayed while flying and believes his name matches that of someone who was put on the list in early 2005.

He called being on the list "a pain in the neck" which "significantly interferes with my travel arrangements".

'Out-of-control'

ACLU said that among those names on the watch list are deceased people, such as Saddam Hussein, the former Iraqi president who was hanged in 2005, as well as decorated war veterans, and Edward Kennedy, the US senator.

Barry Steinhardt, ACLU's technology director, said in a statement: "America's new million-record watch list is a perfect symbol for what's wrong with this administration's approach to security: it's unfair, out-of-control, a waste of resources [and] treats the rights of the innocent as an afterthought."

But the administration of George Bush, the US president, called the list one of the most effective tools implemented after hijacked jets were used in the September 11, 2001, attacks on the World Trade Centre.

The federal "no-fly" list contained just 16 names.

The so-called terrorism screening centre, which maintains the list, has said changes have already been put in place.

Effort made

Chad Kolton, a spokesman for the screening centre, said steps had been taken to ensure the list is accurate and up-to-date.

He cited a report last year by the government accountability office that said there was general agreement within the federal government that the watch list had helped to combat terrorism.

"The list is very effective. In fact it's one of the most effective counterterrorism tools that our country has," he said.

Kolton said that of the individuals on the list, about 95 per cent are not US citizens or residents.