SNP Justice Secretary Humza Yousaf has been ridiculed after hailing a collapse in youth prosecutions and convictions as a “great credit to the justice system”.

Mr Yousaf used Twitter to highlight a fall of nearly 70 per cent in the number of under-21s convicted in the SNP’s first decade in power, despite crime rising.

In the Scottish Legal News, Thomas Ross QC called the comment “mildly extraordinary”, and said the fall in convictions was due to problems in the justice system, not lower crime.

He said: “I appreciate that Mr Yousaf has only been in the job for a month, but measuring the success of the justice system by conviction rates is mildly extraordinary.

“Only two months ago Police Scotland confirmed that crime was on the increase, so it seems unlikely that the public will be impressed by the Cabinet Secretary for Justice presenting a drop in conviction rates as a triumph.

“There can of course be many reasons for a reduction in conviction rates. When accounted for by a drop in crime, everybody welcomes it. When explained by deficiencies in the justice system itself, then the government has to step up.”

Convictions of under-21s fell from 27,832 in 2007 to 8,814 in 2017.

Last year, Holyrood’s justice committee highlighted intense strain on the prosecution service.

However the committee’s SNP deputy convener, Rona Mackay, also praised the figures.

She said last week: “It’s clear that the SNP’s approach to justice is working for communities across Scotland. “To see a fall of nearly 70 per cent in convictions for our young people is absolutely staggering – and it’s no wonder that even the Tories at Westminster are admitting that they ‘have a lot to learn from Scotland’ on issues of crime and justice.”

Labour MSP Daniel Johnson said: “This is deeply embarrassing for Humza Yousaf.

“As Thomas Ross recognises, Mr Yousaf has only been in post for little more than a month, but that is no excuse for making such ill-informed comments.

“The reality is, the SNP has left Police Scotland and prosecutors under-resourced, which has led to falling detection rates and falling conviction rates.

“If Humza Yousaf wants to succeed in his new role he should listen to police and prosecutors – and give them the resources they need to keep people safe.”

A Scottish Government spokesperson said: "Scotland’s firm focus on prevention, responsive policing and local partnerships to help individuals and communities keep themselves safe has had a positive impact on long-term crime trends and people’s feeling of safety, with recorded crime at a 43-year low.

"There has been a 79 per cent reduction in the number of young people prosecuted in Scotland’s courts, an 82 per cent reduction in the number of children referred to the Children’s Reporter on offence grounds and a 77 per cent reduction in the average number of those under 18 in custody since 2005/06.

“While this progress is cause for encouragement, it will never be an excuse for complacency."