The euthanasia campaigner Dr Philip Nitschke has burned his medical practising certificate, and will continue to advise terminally ill patients about how to take their lives.

Nitschke has been embroiled in a fight with the Medical Board of Australia since last year, and says that 25 conditions imposed upon him last month were too onerous and violated free speech.

“The conditions the board sought to impose on me (and by extension, all doctors in Australia) amounts to a heavy-handed and clumsy attempt to restrict the free flow of information on end-of-life choice,” he said, vowing to defy the medical board.

“This is incompatible with the practice of modern medicine.

“Thirty years ago I left the Territory to study medicine in Sydney. Five years later I returned and began my medical career here in this city, in Darwin hospital.

“Today, and with considerable sadness, I announce the end of that 25-year medical career. I confirm this decision by burning my medical practising certificate.”

Nitschke shared his last act as a doctor registered in Australia via Twitter, helping in a medical emergency on board a Qatar airlines flight over the Indian Ocean. He was also called to help a terminally ill passenger on a Qantas flight from Los Angeles to Sydney in June, and despite warning air crew and the man’s family that his medical registration had been suspended, helped stabilise the patient.

Last act as an Australian registered doctor in mid Indian Ocean flight medical emergency, patient doing well! pic.twitter.com/pPWzRDTW5p — Philip Nitschke (@philipnitschke) November 26, 2015

Nitschke, the high-profile head of the euthanasia advocacy group Exit International, has been in and out of court in recent months, challenging complaints against him and the suspension of his medical registration.

Nitschke’s registration was suspended in an emergency meeting of the South Australian Medical Board of Australia in July 2014 after allegations he counselled a 45-year-old man, Nigel Brayley, to take his life. Brayley was depressed but otherwise healthy, and it later emerged he was being investigated in connection to the death of his wife and disappearance of a former girlfriend.

Nitschke has maintained he did nothing wrong, that there was no doctor-patient relationship between he and Brayley, and that he was being made a “scapegoat” by the medical board because it disagreed with his views.

In October the board agreed to lift the suspension but imposed 26 conditions, including that he no longer gave any advice or information to any member of the public, including patients, about how to take their life.

He would also have to refer patients interested in suicide to a registered health practitioner or to a local mental health service, and could only practise under indirect supervision for the next two years.

Nitschke was also specifically banned from providing advice or information about the drug Nembutal, a class of drug known as a barbiturate, which is a sedative that proves fatal at high doses.

“I will remain a doctor and will legitimately use that title, and I will continue to see patients and Exit members in clinics that I run in Australia and other countries,” Nitschke said.

The board had revealed how little insight it had into changing social needs.

“A peaceful death is a fundamental right, this right is not dependent on degrees of sickness, or medical expertise, or any permission or authority that that body can give,” he said.

He will run eight information workshops in every Australian capital over the next two weeks.

“Australia now lags the world ... Australia is becoming something of a basket case in regards to this issue,” he said. “[But] it’s inevitable, legislation will change.”

• Call the crisis support service Lifeline on 13 11 14