Carol and Graham Fisher were shot dead after a struggle

Graham and Carol Fisher were beaten and shot several times at their bungalow next to the Perch Garage near Wadebridge on 5 November.

The Crimestoppers Trust has put up the reward for information leading to the arrest and charging of the killers.

Officers investigating the murder of Mr Fisher, 60, and his 53-year-old wife have not yet identified a motive.

Forensic examinations

Detective Superintendent Stuart Newberry said: "The response from the public has been tremendous, but this extra incentive may persuade those who haven't yet come forward to do so."

Mrs Fisher's younger brother, Nigel, last week spoke for the first time of his grief at the brutal killings.

He said: "It was just a barbaric act. A savage, vicious attack which I can't understand. I can't imagine what Carol and Graham went through."

Detailed forensic examinations are continuing at the murder scene which officers said was left in a "chaotic" state after the attacks.

A 29-year-old man from Exeter and a 45-year-old man from north Devon were arrested in connection with the murders on 19 November and released on police bail the following day.