Pedophile singer Ian Watkins and a girlfriend detailed plans to fall pregnant so they could have a child to abuse in a sex tape, a court has heard.

The video, which was discovered among the jailed Lostprophets frontman's computers and video tapes, was today shown to a jury trying his girlfriend Joanne Mjadzelics, 39, for possessing indecent images.

"While they were having sex they were talking about him getting her pregnant so that they could have a child to abuse," Prosecutor Jim Davies told the court.

The mother-of-one also allegedly spoke of her desire to "play for real" in several online sex chats with Watkins.

During the late-night messages, which had taken place three years after the video was made in May 2011, the pair exchanged indecent images of children and also described the abuse they wanted to inflict on infants and animals.

In one chat Mjadzelics told Watkins, "Part of me feels you get off on showing me stuff you can get away with, knowing that is what I have wanted since forever."

Mjadzelics, of Doncaster, South Yorkshire, described the pair's connection as " deep" and "unmatched" and signed off one message with the phrase "Child molesters till we die".

"I am really happy you now know it is not just talk. The sooner we can be together the better," Watkins replied.

Mjadzelics was arrested as part of Operation Globe, an investigation into Watkins' pedophilia after the singer was jailed for 35 years in 2014.

The court heard there was no dispute that Mjadzelics was in possession of four indecent images of children but kept copies to trap Watkins.

"The law provides a defence to these crimes if the person can show they had a legitimate reason for doing so," Mr Davies said.

"Joanne Mjadzelics says she did have a legitimate reason for possessing and distributing indecent images of children in an attempt to bring Ian Watkins to justice.

"We say that is not the case."

Watkins pleaded guilty, averting a trial at the last minute despite long maintaining his innocence.

He has since complained that he had not realised that his guilty plea had made him "look guilty".

The trial continues.