Locked-in syndrome sufferer Tony Nicklinson's existence of "pure torture" could continue for another 20 years or more if he does not win the right to end his life when he chooses, the High Court heard.

Paul Bowen, QC, for 58-year-old Mr Nicklinson, from Melksham, Wiltshire, told three judges hearing his landmark "right-to-die" case: "Tony has now had almost seven years to contemplate his situation.

"With the continuing benefits of 21st century health and social care his life expectancy can be expected to be normal – another 20 years or more. He does not wish to live that life."

Mr Nicklinson, who suffered a stroke in 2005 while on a business trip to Athens, sums up his existence as "dull, miserable, demeaning, undignified and intolerable".

A "very active and outgoing" man before the stroke, which left him paralysed below the neck and unable to speak, he now communicates by blinking or with limited head movement.

Mr Nicklinson, who wants a doctor to be able lawfully to end his life without fear of prosecution, describes how he has no "privacy or dignity left", and says what he objects to is having his right to choose taken away from him.

Mr Bowen told Lord Justice Toulson, Mr Justice Royce and Mrs Justice Macur that he was being condemned to live in a state of suffering and indignity by the law of assisted suicide and euthanasia.

The law was "anomalous and discriminatory" and had not stopped the "widespread practice of euthanasia, but has forced it underground".

He said Mr Nicklinson was not seeking to persuade the court to "introduce an all-encompassing new regime legalising euthanasia and assisted suicide".

David Perry, QC, for the Ministry of Justice, said Mr Nicklinson's "tragic and very distressing circumstances evoke the deepest sympathy".

However, he added: "Notwithstanding the distressing facts of his situation, the defendant submits the claim for declarations is untenable. The law is well established."