CRIMINALS carrying knives in urban centres face a zero- tolerance approach with maximum sentences raised from one year's imprisonment to four.

The move by the Lord Advocate follows high-profile campaigns by families such as that of Reamonn Gormley, a 19-year-old student stabbed to death in Blantyre last year by Daryn Maxwell, 23, who was on bail at the time of the attack.

The zero-tolerance approach was piloted across Scotland for six weeks over the festive period – between December 12, 2011, and January 23 this year – and saw an 18% reduction in knife crime.

The results also show that almost a third of knife crime and knife carrying took place in town and city centres.

From today, anyone caught with a knife in town and city centres will be prosecuted before a sheriff and a jury, allowing greater sentencing powers with the increase in the maximum term.

The Lord Advocate Frank Mulholland said he was opposed to mandatory sentences for carrying a knife, but the zero-tolerance approach had helped bring about a "very significant" reduction in knife crime.

During the pilot, 212 people were caught carrying knives – 64 of them in a town or city centre – compared to 257 in the same period last year.

Mr Mulholland said: "We said anyone caught with a knife in the town centre would be prosecuted on indictment over the festive period and we said we would review the results of that. Interestingly, it has resulted in an 18% reduction in knife crime over that period. That is very significant.

"Thirty per cent of all of knife crime – possession of knives and assaults involving knives – took place in town and city centres.

"That is from the data over that six-week period and that is further reason for announcing that instead of a pilot this will be policy."

He added: "My son is 13. It'll be a worry when he goes out in the town centre. You want to make these places safer if you can."

Earlier this year, The Herald revealed that crimes involving offensive weapons in Scotland had fallen by almost 40% in the past five years. In 2006-7, there were 10,110 recorded crimes for offensive weapons in Scotland, compared with 6283 in 2010-11.

At the same time, a number of policies have been introduced to tackle knife crime. From June 2006 someone charged with possession of a knife was tried on indictment if they had been imprisoned before.

Prosecutors and police also focused on gangs: from July 2011 anyone caught with a knife on licensed premises or on public transport was prosecuted on indictment if they had been involved in gangs.

The Lord Advocate told The Herald: "The reduction [in crimes] is down to many things, including the strength of the prosecution policy – chances are you might end up in jail – and the huge amount of publicity from victims, the police, campaigners, prosecutors, the media.

"Drink-driving is no longer socially acceptable and neither is racism and we're seeing that knife carrying is no longer socially acceptable."

Although a number of campaigners and politicians have called for mandatory knife sentences, Mr Mulholland is opposed to such a move.

"I've never been a fan of mandatory sentences," he said. "Tough sentences yes, but not mandatory, because there will always be exceptional cases."

Ministers are now looking at ways to allow judges to impose sentences on knife criminals that run consecutively instead of concurrently and at whether those who offend while out on licence – like Maxwell – can be given tougher sentences.

Justice Secretary Kenny MacAskill said: "These are welcome new guidelines from the Lord Advocate which mean even more of these offenders will face the toughest of sentences."