A cooperative which pledged to supply people with a deadly powder and is now under police investigation has cancelled a meeting where supporters could find out more about the chemical mix.

Spokeswoman Petra de Jong told a current affairs show on Thursday night the cooperative had done nothing outside the law but that it first wanted legal clarity.

Some 1,100 members had signed up for the meeting, broadcaster NOS said. ‘We are halting our activities and are not going to do anything illegal. Nor will we inform our members about the powder at a meeting,’ De Jong said.

The public prosecution department said on Wednesday it had begun a criminal investigation into the Last Will cooperative. It is illegal in the Netherlands to help someone commit suicide and doctors may only help carry out euthanasia under strict protocols.

The cooperative hit the headlines last September with the ‘discovery’ of the deadly powder – a widely-available preservative – which is legally available. The group campaigns for the right of people to end their own lives at the time of their choosing.

Earlier this month, it emerged that a 19-year-old woman killed herself using the powder bought on the internet but her supplier is not thought to be the cooperative.