It means staff will work to rule from 1600 GMT, and will carry out a ban on overtime from 2 January.

The action comes after members of theTransport and General Workers Union (TGWU) and Unison rejected the latest offer from West Yorkshire Metropolitan Ambulance Service.

Managers of the service criticised the move and said it will increase pressure on other staff.

'Service jeopardised

Phil Bown, regional industrial organiser for the TGWU, said: "There is a massive shortage of staff at West Yorkshire Ambulance Service, and our members have been run-ragged whilst they are doing their best to serve the public.

"You cannot expect public servants to shoulder the strain indefinitely.

"Despite protracted talks the employers have put no new offer forward. We are at a stalemate."

The unions and employers have been in negotiation for six months about overtime, double pay for bank holidays, and regular breaks for paramedics.

Trevor Molton, chief executive of West Yorkshire Metropolitan Ambulance Service, said: "While we stand by our staff in their concerns over workload, and have done everything within our power to address the issues, we are very disappointed that representatives of Unison and the TGWU have decided to reject the practical solutions offered.

"The action which they propose will serve only to increase the pressures faced by all our staff, and will jeopardise the service which we offer to the public."