Two leading unions, UNISON and Unite, are joining forces to fight plans to privatise the police.
The unions are warning that the £1.5bn contact being advertised by West Midlands to run police services is a dangerous experiment that the public cannot afford to be part of.
The contracts could lead to the privatisation of crime investigation, forensics, 999 call-handling, custody and detention and a wide range of police support services.
Other forces have signed an option to join the Contract at a later stage, adding a potential further £2bn to the privatisation pot and putting more police services at risk.
If all forces joined in the contract, it would place 25% of total police funding into private hands in England and Wales.
Ben Priestley, UNISON National Officer for Police Staff, said: