Mr Ashcroft issued a statement in which he said that if the DEA did have a file "it obviously contains no facts that would sustain a charge" since no charge had been made.
But a newspaper report claimed that official DEA documents made numerous references to Mr Ashcroft and his extensive business interests in Belize and the Caribbean.
He is said to have come under scrutiny as part of four separate investigations dating from the late Eighties to the early Nineties.
The paper said a senior official at the DEA confirmed that Mr Ashcroft had not been personally questioned but that his name, bank and businesses had been tied to their inquiries.
His name appears because of his ownership of the Bank of Belize and the role played by his companies in regulating the country's offshore shipping and financial services industries. It was claimed that at least one of the investigations had a European dimension.
The documents relating to him are allegedly sufficiently substantial for him to be given his own code reference number in the DEA index of individuals and companies to have come under scrutiny.
Mr Ashcroft hinted last night that commercial and political rivals were responsible for the rumours about his business affairs and conceded that he had made enemies. He said: "I make this categorical statement: I have never been involved in drug trafficking or money laundering. My business affairs are entirely proper and no amount of smear, rumour or innuendo will alter that fact.
"I am a tough and determined man and I have made many enemies over the years. I also have many aggressive competitors and am involved in politics, which has always attracted dirty tricks and smear tactics."
Mr Ashcroft has given millions of pounds to the Tory party since William Hague became leader, and he was appointed treasurer last summer despite the misgivings of a number of senior Conservatives.
He has been under increasing pressure this week after inquiries revealed that John Major's government put pressure on the Belize authorities to save him from paying millions of pounds in tax.Reuse content