The Police, Public Order and Criminal Justice Bill, now going through Holyrood, will strengthen police powers of arrest for people suspected of carrying a knife.

But in written evidence to Holyrood’s Justice 2 Committee, which was meeting today, the Association of Scottish Police Superintendents (ASPS) said the provisions did not go far enough in confronting “problems and issues associated with knife crime”.

The ASPS called for mandatory jail terms of 18 months for carrying knives.

“The Executive's proposals show they are tackling knife crime in a determined manner,” said Ms Glen. “That is why the Police Bill will increase the maximum penalty for carrying a knife from two to four years, and raise the age from 16 to 18 on the sale of non-domestic knives. It also why it is granting the police unconditional power to arrest those they suspect of carrying a knife or an offensive weapon.”

But in their written evidence, the ASPS claimed new legislation did not go far enough.

“The Association has previously expressed an opinion that the proposed increase in maximum sentence for conviction on indictment from two to four years will have limited effect, as the vast majority of such offences are dealt with summarily,” said Peter Murphy, the association’s research and development officer.

“The association suggests a provision be included for mandatory sentencing of 18 months jail for conviction on summary for offensive weapon offences.”

He went on, “Parallels may be drawn with the introduction of mandatory minimum sentencing for drink-driving offences, which was seen as a necessary step in influencing driver behaviour in relation to alcohol. It is felt a similar move would contribute substantially in tackling knife crime.”

There were 389 proven cases of knife carrying and possession of an offensive weapon across Tayside between 1999-2003.

The SNP said the police call showed Labour’s claims to be doubling the maximum sentence as “spin without substance”.

Shadow justice minister Kenny MacAskill said, “The new four-year sentence will only apply to the tiny proportion of cases tried on indictment, the more serious form of prosecution. The vast majority of people convicted of possessing a knife currently face a maximum sentence of only six months.”

But he warned mandatory sentences should not be introduced without serious consideration.

“They can cause extreme hardship by severely punishing the foolish as well as the vicious,” said Mr MacAskill. “But if we cannot break the knife culture, there may be little alternative.”