A total of £21.4 million in loans were written off over the Lochaber aluminium smelter

Scottish ministers have written off almost £135 million of public money to help prop up ailing businesses.

The cash put into companies such as Ferguson Marine Engineering, Prestwick airport and Burntisland Fabrications is effectively worthless, according to the national spending watchdog.

Audit Scotland said in a report published yesterday that loans totalling £45 million to Ferguson Marine Engineering had been written off entirely, as was £21.4 million for providing financial guarantees to the Lochaber aluminium smelter. The report also revealed that the government could be exposed to default payments of up to £33 million for the smelter.

A £39.9 million loan to Prestwick was reduced to £6.9 million and an equity stake of £37.4 million in the engineering business Bifab was cut to £2