Scotland's "most dangerous road" must be dualled now to stop more accidents, a Scottish church leader has said.

Professor Donald Macleod, former Principal of the Free Church College in Edinburgh, contrasted the "lavish" multi-million pound upgrade of the M9 Edinburgh to Stirling route, with the lack of investment in the A9, the main north-south route through the Scottish Highlands.

Under current Scottish Government plans, the A9 will not be dualled from Perth to Inverness until 2025.

This is despite the 67 deaths and over 1,200 collisions that occurred on the road in the four years between 2006 and 2010.

Professor Macleod is urging the Scottish Government to dual the A9 "as a matter of urgency", saying the number of people who have died as a result of accidents on the road was "a shame to the nation".

He was writing in the West Highland Free Press following the latest fatal car crash on the A9 earlier this month. The wife and seven-year-old daughter of top Scottish lawyer Andrew Houston were killed in the crash, which happened at a notorious stretch of single-carriageway just south of Ralia, near Newtonmore. The driver of the other car was also killed and Houston and another daughter were seriously injured.

Professor Macleod noted that there were frequent closures of sections of the road because of accidents.

"I'm long past the point where such a warning irritates me. You know at once that you have been merely inconvenienced, while someone else has been struck by tragedy," he said.

Professor Macleod continued: "The Scottish Government refuses to treat the upgrading of this lethal trunk road as a national priority, and Highlanders could just about thole this were it not for what they see as the very different treatment lavished on the central belt: the fortune spent on the grossly under-used M9 between Edinburgh and Stirling, and the billions spent on Edinburgh's trams and the new Forth bridge.

"How many lives will these projects save?"

He added: "The road is notorious, the rate of accidents intolerably high and the cost in human lives a shame to the nation."