Mark Dunne, chairman of Merseyside’s FBU, said: “Rather than wait for the result of the ballot, they have taken four emergency engines to start training strikebreakers.

“They are being stolen from four stations – the city centre and Old Swan which are very busy, Wallasey, our busiest Wirral station, and Crosby.

“All they are doing is depriving the public and it will mean people will have to wait longer for appliances in potentially life-threatening situations.”

The FBU has called on their employers to instead use a reserve pool of up to six appliances to train people ahead of any proposed strike.

But a Merseyside Fire and Rescue spokesman said they preferred to train staff in the engines that would physically be used during any walkout.

And allegations made by the union that managers had warned FBU members they would be permanently lose the four removed appliances, and potentially be moved to different stations, were vehemently denied by the fire service.

The ballot process begins on September 1 and lasts until September 29.

A spokesman for Merseyside Fire and Rescue said: “We’ve taken four appliances off the run as it is a formal requirement to provide resilience since we now have the threat of strike action.”

Fire authority councillor Jack Colbert added: “These vehicles have temporarily been taken off the run to do emergency training.

“It would be remiss of us to not put this in place, and I have assurances they will be put back in service as soon as possible.”