His release after serving 13 months years in jail came when Vienna’s highest court ruled two thirds of the historian’s jail term should be converted into probation.
The 68-year-old said he would call for all historians from Germany and Austria to be boycotted until the nations stopped jailing historians.
Speaking at Heathrow Airport, Mr Irving admitted: ‘On Auschwitz I was mistaken. I said that there were no gas chambers, although that was strictly true because I later discovered evidence that they were in fact just outside the camp.
‘But I now accept that there were gas chambers at Auschwitz. On the overall question, however, I think that historians have been looking at the wrong camps.’
Mr Irving said that the Reinhardt camps were the ‘real killing centres’ but that the Nazis had extinguished all traces of them.
He added that during his court case he was ‘obliged to show remorse’, but he had now ‘decided I have no need any longer to show remorse’.
He said that his experience serving 400 days in ‘solitary confinement’ alongside ‘rapists, bank robbers and car thieves’ meant that he met the sort of people ‘you wouldn’t normally meet’ and saw the sort of things ‘you wouldn’t normally see’.
Irving had been in custody since his November 2005 arrest on charges arising from two speeches he gave in Austria in 1989.
He had been accused of denying the Nazis’ extermination of six million Jews.
He argued that most of those who died at concentration camps, including Auschwitz, succumbed to diseases such as typhus rather than execution.