Worried politicians said they would demand answers from health minister Dr Brian Gibbons -who last week prompted an inquiry into the service after pressing the wrong button during a vote.
Ambulance crews claim the trust's interim chief executive Dr Anton Van Dellen fired off orders "under no circumstance is shift cover overtime to be worked or requested by anyone."
According to a leaked memo only Dr Van Dellen can give permission - or staff will not be paid, even for 999 calls outside their normal working hours.
One paramedic, who wanted to remain anonymous, said during a bank holiday weekend Deeside station - one of North Wales' busiest - had no night cover from 7pm to 7am because bosses refused to pay to cover extra shifts.
Another worker claimed stations at Holyhead, Llangefni, Bangor, Pwllheli and Caernarfon were left with just one paramedic on each shift.
But Welsh Ambulance Trust spokeswoman Claire Russell insisted a daily risk assessment took place to assess the shift cover provided.
"The patient is our priority and that must be central to any decisions we make about staffing," she said.
"The very nature of an ambulance service means that we have to be flexible and responsive to changes in demand.
"However we will not reduce cover below a level that puts lives at risk."
One worried mid Wales paramedic last night warned of the dangers of not covering shifts and having only one paramedic covering huge areas.
He said: "Tywyn was single manned yesterday and Machynl-leth were covering. A letter has now come around saying all overtime must be banned.
"What about the people of Tywyn, which finishes at 3pm? It's not fair on the people. They are not been told the truth about the cover. Places will go uncovered. This is a money-saving exercise. When you consider that the number of calls have increased.
"Somebody will have to die before anybody takes notice. They don't seem to care. They're trying to save money.
"At the end of the day what's the price of somebody's life? Nobody wants that to happen.
"People are asking us why paramedics are turning up on their own. People around here don't call for an ambulance unless they have to".
The memo, from Glyn F Hobby, Powys locality ambulance officer, says: "If stations are requested to cover shifts in or out of hours please make sure that the person making the request has had direct authority from Dr Anton Van Dellen, as the danger is that staff could work the shift and not get paid."
Ms Russell said the trust was "trying to make use of the resources available and that may be reflected in a reduction in the level of overtime required.
"The interim chief executive is the person with the authority to grant overtime and will make that decision in consultation with the relevant managers."
Further claims Dr Van Dellen personally turned down applications for overtime at Llanfyllin, Machynlleth and Llanidloes ambulance stations were denied as "wrong" by Ms Russell.
There were fears the decision meant just three ambulances would cover an area stretching from Aberystwyth to Welshpool.
Last night Plaid Cymru's shadow health minister Helen Mary Jones said: "I am concerned that there is no cover for such a large area in mid Wales. I am demanding a statement from Brian Gibbons next week."
Mid and West Wales Tory AM Glyn Davies said: "It is clearly not a good idea to have an accident or fall into need for an ambulance in mid Wales this weekend because you may have a long wait.
"However, I see no point in blaming this 'skeleton' ambulance cover on Dr Anton Van Dellen, who is now running the service on an interim basis. It may well be that he is under such pressure from the health minister and so short of money that he cannot provide the level of service we all want to see - or restructure the service into one suitable for today."
Dr Van Dellen came to Wales from Staffordshire with his then boss Roger Thayne, to help cover the jobs of top officers Don Page and John Bottel.
But Mr Thayne stepped down after less than three months in the job, claiming 500 lives are needlessly lost each year because ambulances are so poorly-equipped.
Written by Daily Post; Liverpool
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