A son who helped his mother commit suicide at a Swiss clinic has been interviewed by police after a complaint from a relative, it emerged yesterday.

Stefan Sliwinski, 34, was too upset to talk yesterday about his experience following his arrest on Saturday. Mr Sliwinksi, of Clacton-on-Sea, Essex, travelled to Switzerland with his 58-year-old mother Valerie a week ago last Friday. At a clinic run by Dignitas he watched as his mother was given a dose of barbiturates.

Mr Sliwinski has told the BBC he did what he did to help his mother, who had cancer and multiple sclerosis, because she was suffering so much. He said: "She had no quality of life and was in constant pain - and she wanted to die. I went along with my mother's wishes."

But in the aftermath of his trip his mother's sister is understood to have complained to police and Mr Sliwinski was arrested and questioned by detectives.

An Essex police spokeswoman said: "Police arrested a 34-year-old man from Clacton on suspicion of aiding and abetting a suicide. After being questioned he was released on police bail until August 19 for further enquiries."

More than 40 British nationals have travelled to Switzerland to get help to die legally but no relatives have ever been charged despite police inquiries.