A hacker claiming to be in possession of Hillary Clinton's secret emails has threatened to sell them for $500,000, entertainment news publication RadarOnline.com reports.

With recent polling revealing that nearly half of American voters believe that Democratic presidential hopeful Hillary Clinton should suspend her campaign until all the legal issues surrounding her email controversy are resolved, things may be about to get a whole lot worse, with a hacker claiming to be in possession of many of the former Secretary of State's emails threatening to sell them for $500,000.

In an interview for US-based entertainment publication RadarOnline, the hacker said that 32,000 emails from Clinton's private email account are now up for sale to the highest bidder. The publication appears to have taken the computer specialist at his word, saying that he has offered them the subject lines of some of "what appear to be legitimate messages."

The messages include subject lines such as 'H Libya security latest. SID' (with attachment), 'H Algeria latest French Intel on Algeria hostage Sid,' 'H Latest Libya intel internal govt discussions high levels', and 'H HIGHLY IMPORTANT! Comprehensive Intel Report on (with attachment)'.

The hacker explained that while "Hillary or someone from her camp [has since] erased the outbox containing her emails," she or they "forgot to erase the emails that were in her sent box." The source added that "if these emails get out to the public domain, not only is Hillary finished as a potential Presidential nominee, she could put our country's national security at risk."

The scandal surrounding Mrs. Clinton's emails blew up in March 2015, when it was revealed that the former Secretary of State had been conducting official US government business using a private email server between 2009 and 2013.

The Intelligence Community Inspector General has since said that some of these emails contain sensitive information which should have been classified as secret, and that these should not have been sent through an unclassified server. Last month, the FBI launched an investigation into the server's security.

Clinton, presumed the Democratic Party frontrunner, has maintained that she did not transfer classified information via her private server.