Dr Nitschke said London's Metropolitan Police had requested a cautioned interview with him this week and that his lawyers had warned him of a "small but nevertheless possible chance" of being arrested and detained during the meeting.

The founder of voluntary euthanasia group, Exit International, is being pursued over possibly inciting or assisting suicide - an offence that carries a maximum jail term of 14 years in the UK.

It is the strongest action taken by British police against Dr Nitschke who has been running voluntary euthanasia workshops there for years.

While he regularly faces questioning from customs about his intentions when he travels into the UK, Dr Nitschke said he had always been allowed in and out of the country without police involvement.

Dr Nitschke said the British police had indicated a complaint had been made about his 2013 workshop there which was attended by at least 100 people. He suspects the complaint was made by someone from a right to life group.

"They [police] want to talk about the material that was discussed [at the workshop]," he said.

"It comes down to a question of free speech and whether the provision of information was in fact some breach of British law."

Dr Nitschke, who has a PhD in physics, is currently appealing a decision by the Medical Board of Australia to strip him of his ability to practice medicine over his dealings with a man who was physically healthy when he ended his life.

Dr Nitshcke said if a prosecution went ahead in Britain, it would focus on whether his information about suicide laws and methods were in breach of assisted suicide legislation or were consistent with a right to publish such information.

"It would be very much a free speech issue and of course Britain is a signatory to the European Charter of Human Rights which supposedly guarantees free speech. Every politician over here is falling over themselves to talk about how much they treasure and value the concept of free speech in these post-Charlie Hebdo days," he said.

The police interview comes as Dr Nitschke works on a satirical show about euthanasia for the Edinburgh Festival Fringe in August called Dicing with Dr Death.

It also coincides with a court case commencing in Dublin this week over the death of Bernadette Forde, a 51-year-old woman with multiple sclerosis who was a member of Exit when she took her own life with the drug Exit promotes in 2011.

One of Ms Forde's carers, Gail O'Rorke, has been charged with "aiding and abetting, counselling or procuring" her suicide. It is not clear what the police allege Ms O'Rorke actually did before Ms Forde took her life or was in the process of ending her life.

Dr Nitschke said although he had spoken with Ms Forde about her decisions over the phone, he had not been questioned by police over her death.

While Britain has allowed more liberal publication of Dr Nitschke's book The Peaceful Pill Handbook than Australian authorities, he is concerned it seems easier to become ensnarled in British laws around suicide compared to in Australia.

"The mere provision of information that could facilitate this [suicide] could be in breach. That's never been tried in Australia," he said.

"Our argument has always been that provision of good information allows people to make informed choices either this way or that way, it doesn't propel people down the suicide path."