SNP ministers are under pressure over their “mismanagement” of Scotland’s NHS after it emerged the number of patients being sent to other parts of the UK for specialist treatment has increased by almost 50 per cent.

The Liberal Democrats urged Shona Robison, the Health Minister, to explain why the number of Scots referred for treatment to England, Wales or Northern Ireland increased from 427 in 2013/14 to 625 in 2016/17.

Over the same period the cost of referring patients to hospitals in other parts of the UK has increased from £11.9 million to £15.2 million. The total bill for the Scottish NHS over the past four years has reached £51.7 million.

The disclosure came amid mounting criticism of the SNP government’s NHS workforce planning, with official figures published earlier this month showing nursing and consultant vacancies at a record high.

The British Medical Association said the 460 unfilled consultant posts were “inevitably having a significant effect”, with nearly half the positions lying empty for more than six months. It also emerged that more than 400 vacancies were cancelled in July, the equivalent of around one in 12.

In a further sign of the increasing pressure on Scotland’s NHS, it also emerged that the number of prescriptions for dementia drugs das almost doubled in seven years.