Conservative Party chairman Grant Shapps has admitted that he did work as a web marketer under a pseudonym after entering Parliament.
A recording from 2006, a year after Shapps was elected, shows the MP selling a business self-help guide calling Stinking Rich 3 and claiming his products could make listeners a "ton of cash by Christmas", according to the Guardian.
Shapps used to run the HowToCorp website, which featured get-rich-quick advice from the supposedly successful businessmen Sebastian Fox and Michael Green - a name the Conservative used as a business alias.
In the recording Shapps, under the pseudonym Green, can be heard telling a fellow entrepreneur that the guide "is not a cheap product, but it's a great internet marketing product".
Asked last month on LBC whether he had second job, Shapps replied, "To be absolutely clear I don't have a second job and I have never had a second job whilst being an MP. End of story."
But now the Conservatives say that although the chairman had talked of his writing career having ended when he became an MP "in fact it ended shortly afterwards".
Shapps has insisted it was an "old story" and his business dealings had all been properly declared.
Labour has called for Prime Minister David Cameron to launch an investigation to "establish all the facts".
"It seems that Mr Shapps' repeated denials, which were not in the heat of the moment but also included a calculated decision to instruct solicitors, were contrary to the facts," shadow solicitor general Karl Turner said.
A Conservative party spokesman said Shapps had written with a pen name "like many authors and journalists".
"This was completely transparent: his full name and biographical details were permanently published on the company's main website," he added.