The Amicus union is balloting some 400 members about striking over a management plan to alter its pensions provision for workers.

Peter Coulson, from the union, said it had "spent two years negotiating with the company to no avail".

Birmingham Airport said negotiations with the union were continuing.

The ballot of Amicus members will begin on Tuesday. Airport firefighters and engineers will be balloted separately.

Strike action could close the airport during one of its busiest seasons, because under Civil Aviation Authority regulations an airport cannot operate without the fire service.

It is understood the airport's management plans to close its pension scheme to new members and replace it with one which would give lower returns.