Firefighters may take strike action over plans to make them work until they are 60.
The Fire Brigades Union is consulting its members over a ballot on industrial action.
Crews may join thousands of other public workers in downing tools during the TUC’s day of action on March 28.
Firefighters are unhappy about plans to raise their retirement age from 50 to 60 and changes which will trigger increased pension contributions.
FBU General Secretary Matt Wrack said: “These are unfair and unaffordable contribution hikes.
“There is a real danger they will trigger an exodus from the scheme. That means a drop in the money coming and less to pay for pensions going out.”
And Mr Wrack branded a pensionable age of 60 as “unrealistic”, adding: “Everyone is saying that 60-year-olds can’t work as frontline fire crews.”
But he stressed that the union was still in active discussions with the Government and did not want to strike.
“We never rush into a ballot for action and have constructively engaged in all talks,” he said.
No-one was available for comment from the West Midlands branch of the FBU. But the chairman of the region’s fire authority, Coun John Edwards, said he would be “disappointed” if crews took strike action.
“We are being dragged into this dispute which is not a problem of the West Midlands’ making,” he said.
The pension changes would see firefighters pay 14.2 per cent of their salary into their pension scheme, up from the current 11 per cent.