Holocaust denial is slowly becoming a thing of the past, according to a leading authority who claims there are only three or four "pure denial experts".

Dr Nicholas Terry, founder of the anti-denial blog Holocaust Controversies, told a Leicester University conference that denial these days has "great brand recognition, but almost zero customers".

Dr Terry, a historian at Exeter University, said: "My assessment is that there have been around 100 authors since the 1940s who have written what can be considered pure denial books or pamphlets.

"Most of these experts are now either dead or inactive. It's down to only three or four authors who are capable of writing such books."

He said there are another 100 cheerleaders or propagandists who talk down the Holocaust but without contributing original ideas. These include Iranian President Mahmoud Ahmadinejad and 500 "footsoldiers" who are active online.

The reason for the decline in experts is "generational", he said.

"The big names of the eighties and nineties are mostly over 60. Very few under-60s are stepping up to replace them.

He said the Irving-Lipstadt case in 2000, where David Irving lost a libel suit against author Deborah Lipstadt for calling him a denier, had "severely downsized" the movement.

He said the hearing led to the suspension of the Journal of Historical Review, the movement's former flagship, and the withdrawal from activity of many experts.

He also said that web traffic for denier forums was small. Other conspiracy theories have been more prevalent in the past 10 years, particularly since 9/11.

But Dr James Smith, chairman of the Beth Shalom Holocaust Centre, warned of the continuing danger.

"The problem is, even after professional Holocaust deniers have died, their published material remains in circulation, is available on the internet and remains as pernicious and dangerous as ever," he added.

Mark Gardner, of the Community Security Trust, said that while legal action in many countries had limited the growth of Holocaust denial,
"as a global issue", he added: "We
need to pay serious attention to
denial throughout the Muslim world; and forms of denial in the ex-Soviet bloc."