Membership of a group campaigning for the right of people to end their own lives at the time of their choosing has doubled following a television programme about its ‘discovery’ of a deadly powder which is legally available.

The Last Will cooperative had 3,323 members before the Nieuwsuur broadcast but membership has now rocketed to 6,800, chairman Jos van Wijk told local paper De Stentor.

The cooperative is campaigning for the right of its members to obtain and use a drug to end their lives at the moment they see fit. New members have to wait six months before they are given information about the powder, which is a widely-available preservative.

Van Wijk said the group came across the substance, which he refuses to name, after talking to chemists, pharmacists and toxicologists who are members of the organisation. ‘We were looking for something which is legally available,’ he said. ‘You cannot buy it in shops but it can be bought online.’

Despite the surge in membership, the cooperative has come under fire for allowing people as young as 18 to join and for breaking the law which bans people from helping others to commit suicide.