Keith Farnham
Investigation: Illinois state representative Keith Farnham, pictured when he announced his resignation on March 19, is facing child porn charges

Illinois representative Keith Farnham has been charged with using state and personal computers to trade child pornography.

The 66-year-old allegedly boasted about molesting a six-year-old girl and used online chat rooms to discuss his fantasies.

When he resigned on March 19, one week after his Elgin office and home were raided, he claimed he was standing down because of health concerns.

On Monday the Democrat, who twice sponsored Bills to impose stricter sentences on pedophiles, was accused of using online chat rooms to trade images and videos of child abuse.

Authorities linked a Yahoo! email account used by the married father-of-one to an online trading forum, the Chicago Tribune reported.

In one online conversation in November, Farnham allegedly described molesting a six-year-old girl and having sexual intercourse with the child's mother while the girl watched.

The retired Navy veteran is not currently facing charges over the alleged encounter.

In other online chats linked to his email address, the state representative allegedly discussed videos that were being shared.

According to the affidavit, in one message he allegedly said: '12 is about as old as I can handle. I love them at 6 7 8.'

The affidavit claims that between August 2013 and January of this year, hundreds of images and video, including one of a six-month-old baby being abused, were shared from the email address.

Several attachments, showing young girls being forced to perform sex acts on adult men, were allegedly sent from Farnham's state office computer.

One piece of equipment seized was marked 'Property of the State of Illinois House of Representatives'.

Farnham was investigated after an anonymous tip to homeland security agents. A search of the email address allegedly used by the state represenative revealed the files and graphic chats with at least three other individuals.

The internet activity was traced to an account at Farnham's home.

According to My Fox Chicago, some of the conversations Farnham allegedly had were with an undercover agent posing as a chat room user.

The agent was also the person to whom sick videos of child abuse were later emailed.

When Farnham resigned last month he said: 'I have been battling serious health issues for a number of years, and the coming months will require my full attention.'

He had represented Illinois since 2009 and was chair of the Government Relations Committee, according to his candidate biography.

The state representative had championed two Bills for tougher sentencing on child pornography in recent years, including one calling for harsher penalties when the victims are under 13.

Farnham, who is due in court on Wednesday, has not responded to media requests for comment.