Ian John McLoughlin, 55, was jailed for life in 1992 for the murder of Brighton barman, Peter Halls, in September 1990, and it is believed that he still has contacts in Sussex.
Detective chief inspector Martin Brunning, from the Bedfordshire, Cambridgeshire and Hertfordshire major crime unit, said: “We urgently want to speak to Ian McLoughlin in connection with this offence.
“We believe that he is possession of a large amount of £50 and £20 notes which he may be using for purchases. It is a substantial amount which he could be trying to conceal.”
Chief Superintendent Steve Barry, from Sussex Police, said: “We are working with colleagues in Hertfordshire in a bid to trace this man. There is no specific information to suggest that he is in Sussex, but we would ask anyone who spots him or knows of his whereabouts to dial 999 immediately.
“Do not approach him. He is a very dangerous man.”
McLoughlin is described as white, about 6’, with straight, greying, collar length hair.
On Saturday, he was believed to be wearing sunglasses, blue jeans or three-quarter-length trousers and a blue-and-white checked short-sleeved shirt with a button-down collar.
He also uses the name Ian John Baker.
He should not be approached under any circumstances.