The trust says careful planning can make overtime unnecessary

The papers show three of five ambulance stations in north Powys will be out of action, after overtime was refused.

The Welsh Ambulance Trust has denied an overtime ban is in place or that any station would close. It said that it was looking for staff to cover shifts.

Mid and West Wales AM Glyn Davies described issues over ambulance cover and staff morale as "very worrying".

It is the latest controversy to hit the service which is to be the subject of a public inquiry after the health minister voted for the move by mistake.

The stations at Llanfyllin, Machynlleth, and Llanidloes will be affected, according to the documents.

The papers seen by BBC Wales show that the interim chief executive of the Welsh ambulance service trust, Dr Anton Van Dellen has personally turned down application for overtime at the three stations.

I'm desperately hoping that nobody who is part of my family will be ill or in need of an ambulance this weekend AM Glyn Davies

The papers claimed the decision meant just three ambulances would cover an area from mid Wales stretching from Aberystwyth to Welshpool.

The trust said on Friday none of the three ambulance stations would be closed and it was actively seeking staff to cover weekend shifts.

Ambulance workers have raised fears about the level of cover available in mid Wales to BBC Wales, and also claimed morale in the service is at rock bottom.

Conservative AM for Mid and West Wales, Glyn Davies, told BBC Wales both the skeleton cover and the morale issue were "worrying".

"It seems that three ambulances to cover the whole of mid Wales is very sparse," Mr Davies said.

"Even more worrying is that staff morale appears so low that they are contacting the BBC."

Dr Gibbons accidentally voted the wrong way in this week's debate

Mr Davies said he was "hesitant" to criticise the decision to stop overtime until he knew what was behind it.

"What I do know is that the outgoing chief executive has said that he was ashamed of the service that was putting 500 lives at risk per annum in Wales."

Plaid Cymru's health spokeswoman Helen Mary Jones said she would demand a statement from health minister Dr Brian Gibbons next week.

She said: "Plaid secured a public inquiry...earlier this week in order for the public to have confidence in their ambulance service. I am concerned that there is no cover for such a large area in mid Wales".

A spokesman for the Welsh Ambulance Trust denied that there was a ban on overtime in place.

He said the trust was trying to make better use of the resources it has available - and said that could be reflected in a reduction in the amount of overtime that was needed.

'Simple remedy'

The spokesman said careful planning can mean all areas are covered without the need to resort to unnecessary overtime.

He added that the trust's priority was always patient care and any concerns about lack of cover are groundless.

Meanwhile, assembly presiding officer Lord Dafydd Elis-Thomas has offered a solution to the voting mistake which allowed a public inquiry.

On Tuesday, Dr Gibbons pressed the wrong button which led to him voting in favour of an opposition motion.

Lord Elis-Thomas told BBC Wales the error could be corrected easily.

He said: "There is a simple remedy for the government, and I am surprised they didn't take it the following day, and, that is a motion to rescind. I'm waiting for it."