Campaigners fighting to save an emergency operations centre in Worcestershire yesterday launched a bid to take the region's ambulance service to a judicial review.
A "letter before claim" was sent to West Midlands Ambulance Service's headquarters in Brierley Hill yesterday morning.
It claims the decision taken on November 28, 2007, to close its 999 call centre at Bransford, near Worcester, was "unlawful" and "likely to result in a court quashing the decision".
Leigh Day & Co law firm, which served the papers, were instructed by Clare Boorman, who lives in Malvern, Worcestershire.
Ms Boorman, who suffers from a schizoaffective disorder, took a potential overdose in 2004 and needed emergency treatment.
An ambulance arrived in time to take her to hospital but, after making a full recovery, she was told if crews had been delayed she would have almost certainly died.
In the papers, Rosa Curling, at Leigh Day, states: "It is for this reason that she is extremely concerned about your proposal to close down the EOC at Bransford, a decision that we do not consider lawful."
It suggests WMAS's consultation over the reconfiguration of emergency call centres, and its decision to close facilities at Bransford and Shrewsbury, Shropshire, is unlawful on grounds of "legitimate expectation" and "unlawful consultation".
Prior to the national reorganisation of ambulance trusts in 2006, Hereford and Worcester Ambulance Service and the enlarged West Midlands trust had agreed Bransford would not close.
Ms Curling adds the trust's decision is "in breach of this agreement and the public's legitimate expectation and is consequently unlawful".
"We are informed that the financial analysis of the alternatives was completed in private and the Board rejected all 13 alternative options without detailed reasoning. Again, this is unlawful."
If a judicial review is held, campaigners will have to find £5,000, a quarter of the expected £20,000 costs, the remainder of which are set to be met by legal aid.
Richard Burt, Lib Dem prospective parliamentary candidate for West Worcestershire, said the consultation process was "nothing more than a roadshow to publicise a single, preferred option".
He added: "I don't think they were prepared for this level of opposition, and I think this legal action will have surprised them."
Last night a WMAS spokesman confirmed it had received correspondence "in regard to the decision to close two EOCs".
He added: "The letter has been passed to the trust's legal advisers. The trust remains convinced that its proposals will lead to a better level of patient care for members of the public right across the region."