Five MOD scientists will be arrested this week over their alleged roll in horrifying experiments carried out on volunteers at the top secret Porton Down research centre.

  In an unprecedented move the civil servants face a criminal probe into claims of assault, wounding and administration of poison.

  The five men some of whom are retired, will be formally interviewed in the presence of their solicitors on Wednesday and Thursday. The scientists were involved in the mass testing of chemical and biological weapons on volunteers who thought they were taking part in research into the common cold, from the 50's to 1989.

  The decision to quiz the men comes at the end of the 18 month operation antler enquiry by Wiltshire police. Officers have been investigating the deaths of more than 40 volunteers and injuries to more than 400 others at the centre near Salisbury. 77 ex-forces personnel are seeking compensation for illnesses and Ken Earl of the Porton Down support group said. 'I hope those responsible for the deaths of innocent service men are brought to justice. I was a medic and took part because I thought it was research into the common cold. Instead I had sarin, the most deadly compound known to man, drooped on my arm.'

  A spokesman for the MOD said last night. "The MOD has always been as helpful and co-operative as possible with the police enquiry."