The insider, who is reportedly well connected within the hacking community, told Sky News that The Impact Team are "just bluffing" about leaking the data.
"They claim that they are going to give all the information out, especially credit card details and all the other 'links' and the 'hashes'," the anonymous hacker told Sky.
"I don’t think they're going to release them.
"They have a better chance of selling on to someone else or to a 'Blackcat Market' on the 'Deep Web'. They’ll profit from this in a big way, especially with the size of this database."
In a statement, Ashley Madison parent company Avid Life Media said: "We were recently made aware of an attempt by an unauthorised party to gain access to our systems.
"We immediately launched a thorough investigation utilising leading forensics experts and other security professionals to determine the origin, nature, and scope of this incident.
"We apologise for this unprovoked and criminal intrusion into our customers' information.
"The current business world has proven to be one in which no company's online assets are safe from cyber-vandalism, with Avid Life Media being only the latest among many companies to have been attacked, despite investing in the latest privacy and security technologies.
"We have always had the confidentiality of our customers' information foremost in our minds, and have had stringent security measures in place, including working with leading IT vendors from around the world.
"As other companies have experienced, these security measures have unfortunately not prevented this attack to our system.
"At this time, we have been able to secure our sites, and close the unauthorised access points.
"We are working with law enforcement agencies, which are investigating this criminal act.
"Any and all parties responsible for this act of cyber–terrorism will be held responsible."
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