People were led from the building during the exercise

The Fire Brigades Union Scotland said it had concerns for members' safety.

It claimed the brigade had not properly completed risk assessments, but senior brigade officers said union officials had been consulted during the planning.

The firefighters had been due to rescue "casualties" from a building at Dundee Harbour after a simulated attack.

The FBU denied its opposition was related to the recent dispute in Manchester over new equipment.

The risk assessments are some of the worst I have seen in 14 years of being a safety representative Kenny Ross FBU

The union's Scottish secretary Kenny Ross instead dismissed the exercise as a waste of time.

He said: "We are quite happy to take part in this kind of exercise as long as the proper preparations have been done.

"We have serious and genuine concerns over health and safety and believe this exercise should not go ahead.

"The risk assessments are some of the worst I have seen in 14 years of being a safety representative, they are amateurish and the preparations, both within Tayside and inter-agency, are ridiculous. It's an absolute shambles."

Denying the decision was a political one, he added: "To go ahead with the exercise without any fire service involvement makes a mockery of the whole thing."

Organisers 'disappointed'

Fire crews were supposed to have performed the search and rescue of "contaminated survivors" - about 150 local volunteers - from a building.

Fire chiefs said they were "disappointed" crews did not take part.

Tuesday's anti-terrorist exercise went ahead with principal fire brigade officers working alongside the other emergency services.

Tayside Police Assistant Chief Constable Willie Bald said the exercise had been a success.

A man is sprayed after the mock chemical attack in Dundee

"The whole purpose of today was finding out how to deal with large numbers of people, what's involved in that and how we would work together," he said.

"So it's been very successful from that perspective."

Hundreds of doctors, nurses, ambulance staff, GPs, firefighters and police officers took part in a mock chemical attack in Newcastle last month.

The test involved a simulated chemical gas attack on a crowded city centre theatre.

Renewed tensions between firefighters and employers have been in evidence in recent weeks.

Fire crews expected a pay rise in November after agreements made last June for a staged 16% increase, which was aimed at settling the previous year's nationwide pay dispute.

But the FBU has withdrawn from the deal, saying the money has still not been delivered.