Lawyers for psychic performer Sally Morgan have said she will not take the scientific test scheduled to coincide with Halloween

Sally Morgan, the TV clairvoyant who styles herself as "Britain's best-loved psychic", has turned down an invitation to prove her supernatural powers on Monday.

Morgan, who claims to converse with the spirit world in sellout shows across the country, was asked to demonstrate her abilities in a Halloween challenge laid down by sceptics in Liverpool.

Morgan's lawyers, Atkins Thomson, emailed the science writer Simon Singh, who organised the scientific test of her powers, to make clear that she would not take up the challenge.

The email, from Graham Atkins, requests that Singh does not contact Morgan or her office again, and states: "You well know that we all have far more important things to do than take part in this or any other 'test' at this point. She will not attend at Liverpool or at any other time."

The email was marked "strictly private and confidential – not for publication", but after seeking independent legal advice, Singh posted the correspondence with a response on his blog.

Sceptic groups planned the test after Morgan's live show in Dublin last month at which some members of the audience reported hearing someone apparently feeding Morgan information on stage.

Morgan, who claims to have seen her first ghost at the age of four, has strongly denied any fakery and said the voices were theatre technicians chatting. The theatre supported this account in a separate statement.

Had Morgan accepted the challenge, she would have been shown pictures of 10 dead women and asked to match them to a list of their first names. The offer to take the test remains open and Morgan has been invited to discuss changes to the challenge with the group.

The US paranormal investigator James Randi backed the experiment, which qualified as a first step towards a million-dollar prize established by the James Randi Educational Foundation for any psychic who can prove their special "gift" to be real.

The test was devised by Professor Chris French, head of the Anomalistic Psychology Research Unit at Goldsmiths, University of London, and was due to be hosted by the Merseyside Skeptics Society.

Singh said on Monday that he had received several more emails from Morgan's lawyers. He added that the Halloween challenge will become an annual event for psychics and others who claim supernatural abilities.

Update: On 20 June 2013 Sally Morgan successfully settled her libel action against publishers of the Daily Mail, who withdrew the suggestion that she used a secret earpiece at her Dublin show in September 2011 to receive messages from off-stage, thereby cheating her audience, and accepted that the allegation is untrue. Her statement can be found here.