Government secrecy would put thousands of additional lives at risk in a biological terror attack, an Oxfordshire emergency expert has warned.

A masked participant in a recent terror attack exercise

County emergency planning officer John Kelly has helped conduct two exercises simulating biological attacks in the past six months.

He claims that if they had been real, tens of thousands would have been contaminated. The Home Office policy was to keep the press and public "in the dark" in the event of a national emergency - despite Government guidelines apparently promising instant advice via the media.

As part of the second exercise, carried out in the Bicester and Upper Heyford area, the Home Secretary ordered an information blackout.

"We were forbidden from getting the people on side, working through the media, and it was 18 hours before the Cabinet Office gave the all-clear for us to break cover," said Mr Kelly.

"By that time, if we hadn't just been rehearsing, 30,000 people around Bicester would have been wiped out - all because they would have been denied the chance to evacuate.

"Earlier, in November, we weren't allowed to advise the public for 12 hours during a dummy run reaction to a plague incident."

This is exactly how the people paid to protect the population of Oxfordshire would have to behave in a real biological or chemical terrorist attack. Mr Kelly also believe that the Government should provide more funding to fight the increasing threat of terrorist attacks. Oxfordshire County Council spends £100,000 on emergency planning.

Mr Kelly claims that a national warning system is needed but that it will not be brought in because the policy of secrecy was rooted in the "Cold War" of the 1950s and 60s.

A Home Office spokesman said: "This really comes under the responsibility of the Cabinet Office, although we do have a role to play, of course. Whatever instructions we pass on have been formulated and approved by the Cabinet Office."

However, the Home Office website says: "The authorities will use local radio and TV to deliver information and advice.

"Public safety is our absolute priority in all decisions about public information or warnings.

"To give detailed advice in advance about how to handle every potential threat would be misleading and unhelpful. Worse, it could lead to confusion in an actual incident."

Cabinet Office spokeswoman Katherine Fisher said: "The Government and the emergency services will provide immediate information and advice in the event of a discernible threat or a specific incident. The Government's advice to anyone involved in a major or catastrophic incident is 'Go in, stay in, tune in'.

"As would be expected, the Government are continuously reviewing the best way to keep the public informed."