OVERTIME payments to consultants is soaring as hospitals come under growing staffing pressures, an investigation has found.

A probe of NHS boards across the UK has found Scotland's health boards have paid out more than £20m in overtime and additional pay to some medics in the past year, a rise of around 50 per cent.

Responses to freedom of information requests by 12 of the country's 14 health boards showed spending going up from £14.27m in 2013/14 to £20.92m in 2015/16.

Scotland's health secretary Shona Robison said overtime was a "tiny percentage" of the overall spend on consultants and said the government was "determined to eradicate high cost overtime payments in NHS Scotland".

But the body representing the UK's doctors said the payments were the result of a shortage of consultants.

Dr Peter Bennie, chair of the BMA in Scotland, said: "The overall picture here is the straightforward issue of there simply not being enough consultants on the ground to do the jobs."

The BBC asked all 186 organisations running NHS hospitals in the UK about overtime and extra payments over the last three years.

Across the UK, overtime and additional payments have increased by more than a third, to £168m, in 2015/16, with one doctor in Lancashire making almost £375,000 in the space of 12 months.

Consultants doing overtime commonly make £600 for a four-hour shift, three to four times their normal rates, while overtime for urgent and emergency work tends to be around £300 per shift.

NHS Grampian had the greatest increase in payments in Scotland, from zero in 2013/14 to £1.6m two years later, with sharp hikes also at NHS Lanarkshire, from £1.8m to £3.4m, and NHS Lothian, from £1.3m to £2.1m.

But Dr Bennie added that 162 consultancy posts had been empty for six months of more, claiming this alone represented approximately £15m not currently being paid by health boards.

He said: "That balances out quite a bit of this. The main figure that is being quoted is £600 for four hours work. That's four hours of work, almost always at weekends or late into the night.

"That's working out to about £85 an hour after tax and it seems to be that that is not at all extortionate for a group of the most highly-trained and most expert people we have in the country in the health service."

Ms Robison said there would be a "number of reasons" for the increase in overtime costs.

She told BBC Scotland: "Clearly we have some gaps in certain specialities which are hard to fill.

"Sometimes there are vacancies which take a while to fill and there are sickness and maternity issues to cover, so boards sometimes do have to use people on a short-term basis.

"I also think its important to put that in a bit of perspective in that the figure spent on consultant overtime payments does represent a small fraction of the overall cost of consultant staff, less than 3 pert cent of the £720m a year that we spend on consultant medical staff.

"So, this represents a small amount, but clearly something we need to tackle and something we are determined to tackle."

Scottish Conservative health spokesman Donald Cameron said the payments reflected a "deep systemic problem" in the NHS.

He added: "These are very disturbing figures. Not so much because of the sums that are being earned by consultants but more because it demonstrates very starkly that there are growing pressures on our hospitals and not enough staff to cope.

"Not less than a year ago it emerged that there was a mini retirement boom amongst consultants and many consultant vacancies are unfilled in Scotland."