THE Government last night revealed plans to challenge the verdict of an inquest which ruled that a North-East airman was unlawfully killed more than 50 years ago.

Leading Aircraftman Ronald Maddison died during secret nerve gas experiments at the Porton Down chemical warfare testing facility in Wiltshire.

His family has battled since 1953 to find out how he died, and last month thought their fight for justice was over when a second inquest returned a verdict of unlawful killing.

They now plan to sue the Ministry of Defence for compensation in a case which could pave the way for hundreds of other servicemen who were subject to experiments at the site between 1939 and 1989.

The MoD yesterday apologised to Mr Maddison's family and said they would "look favourably" upon any bid for compensation but said they would be seeking a judicial review to overturn the inquest ruling.

Mr Maddison, an RAF technician from Consett, County Durham, died aged 20 after having drops of sarin dabbed on his arm.

Winston Churchill's government ordered the initial inquest into Mr Maddison's death, which reached a verdict of misadventure, to be held in secret.

After years of campaigning by the family, an inquiry was launched by Wiltshire Police in 1999 and in 2002 Lord Chief Justice Woolf granted permission for a second inquest, which began in May this year.

The 64-day hearing ended last month with Mr Maddison's family claiming their long search for the truth was finally over.

But last night, a former RAF serviceman who underwent the same sarin test as Mr Maddison, said he was ''horrified'' at the MoD's challenge.

Ken Earl, 71, from Maidstone, Kent, said: ''I'm flabbergasted that they could even think about it - it's unbelievable."

A statement from the family's solicitor, Alan Care, said: "We are pleased that MoD have at long last apologised to the Maddison family following our two letters to the Prime Minister requesting his personal apology and that the MoD will favourably consider compensation given an acknowledgement of negligence in causing the death of Ronald Maddison.

"However it is with absolute astonishment that we see that MoD intend to challenge by way of judicial review the inquest verdict after all the jury heard more than 60 days of evidence from over 100 witnesses and the jury's unlawful killing verdict was unanimous. The MoD seems to be clutching at the thinnest of straws.

Former Royal Navy serviceman Eric Gow, 69, from Merseyside, who was tested at the base in January 1954 and now runs the Porton Down Veterans Support Group, said: ''After the verdict was recorded, the Maddison family would have expected not to have to continue fighting.

''It's such a shame that they have to. In fact the shame lies with the Government.''

Defence Minister Ivor Caplin said yesterday that he had now written to the Maddison family apologising for the fact that the test had been carried out, even though an identical test two days earlier had resulted in an adverse blood test result in one serviceman.

''Any claim for compensation from his family would be considered favourably on the basis of the negligence referred to above,'' he said.

During last month's inquest, Mr Maddison's family claimed he and other military personnel were tricked into taking part in what they believed were harmless experiments to find a cure for the common cold.

The court heard how the test that claimed his life was carried out just nine days after a similar experiment resulted in the near-fatal poisoning of another volunteer, soldier James Kelly.

But lawyers for the MoD said all servicemen who underwent chemical experiments at Porton Down were told beforehand.