Two health boards in Scotland have seen more than 20 per cent of their consultant posts unfilled, doctors' leaders have warned MSPs.

Jill Vickerman, Scottish secretary of the British Medical Association (BMA), also claimed that there was "a weekly crisis" in the health service over staffing for GP out-of-hours care and hospital accident-and-emergency units.

She made the comments after Andrew Walker, a health economist from Glasgow University, said he was "optimistic" that the NHS was sustainable.

But Ms Vickerman said that doctors were currently facing "some very specific and new problems which are hugely concerning".

She told MSPs on Holyrood's Health and Sport Committee: "We have in two of the health board areas over 20 per cent vacancies in consultants, we've never seen anything at that level before.

"We have a weekly crisis to deal with in terms of whether or not GP out-of-hours and accident-and-emergency units are going to be properly staffed."

Mr Walker, however, told the committee he had spent almost 25 years studying the health service and concerns being raised now were similar to those raised two decades ago.

He said: "You could find almost exactly the same speeches in the 1990s that we're hearing today, about how it won't last much longer."