Joanne Mathers, a 29-year-old mother of one, was shot dead by the IRA on the doorstep of a house in the Gobnascale area of the Waterside while out collecting census forms on 7 April 1981.

Her killer or killers have never been found.

To coincide with the 31st anniversary of Ms Mathers' death, her husband Lowry is offering the reward in a bid to bring those responsible to justice.

"I want justice for Joanne, even after all these years. I hope the reward will encourage someone with information to come forward and tell Crimestoppers what they know," he said.

The reward is being offered through the independent charity Crimestoppers UK and is accessible to anyone who passes on information anonymously that leads to an arrest and conviction.

Mrs Mathers' son Shane was just two at the time of her murder.

He said those involved with his mother's death will "never know the pain" he and his father have gone through.

"I never really knew my mother because she was taken away from me far too early.

"While our family appreciates that nothing will bring my mum back, we want those responsible for her murder to be found and brought to justice.

He continued: "I am reaching out to anyone who might have information to contact Crimestoppers anonymously, because it might be key in helping to catch those who committed this crime."

SDLP MP for the area Mark Durkan said he supports the Mathers family in their appeal.

"This appeal demonstrates their continuing pain and continuing need - like so many other families who have lost loved ones during the course of the Troubles. It is important that they realise they are not alone.

Gregory Campbell, DUP MP, added that it was a "cold-blooded" murder.

"At the time the Republican movement were campaigning against the Census," he said, "It was widely believed that the IRA was responsible."

"Somebody somewhere 31 years ago knew something, and many of those people are still alive today and somebody should forward to allow the Mathers family to see some closure."