Conservative leadership contender Kenneth Clarke has hit back at "fanatic" anti-smoking campaigners and Guardian allegations of cigarette smuggling by British American Tobacco.

A "whistleblower" has claimed that BAT ran a global smuggling network worth hundreds of millions of pounds via a shadowy Swiss subsidiary and bank account. The allegations have renewed the controversy over Clarke's tenure as deputy chairman of the tobacco company.

The timing of the allegations has, Clarke believes, been deliberately engineered to give the anti-tobacco lobby headlines at the height of the Conservative leadership campaign and he attacked "opportunist" Iain Duncan Smith supporters in the press.

Clarke said that behind the latest BAT row was "the more fanatic end of the anti-tobacco lobby who think that the leadership election is a good opportunity to give it a whirl and some of the more fanatic of Iain Duncan Smith's supporters in the press who think that it is a good opportunity to bring this out on the day that the membership are getting their ballot papers''.

Defending BAT as a "reputable company", Clarke backed evidence he gave to MPs on the Commons health select committee in February.

"There is nothing wrong with my continued assurance that BAT does not organise smuggling," he said.

A BAT spokesman told ePolitix.com that "there was nothing new about the story which is a variation of old allegations that the company is involved with smuggling".

"Our reply is the same as. We don't smuggle or condone it. This story is only news because of the Conservative leadership campaign. A DTI inquiry is ongoing, what else is there to say?," he said.