Shopkeepers caught selling knives to children should face tougher penalties, Solhull MP Lorely Burt has insisted.
Ms Burt (Lib Dem) called for more retailers to go to jail, after the Home Office announced plans for a major crackdown on under-age sales.
Children are be recruited by police and trading standards officers to catch shopkeepers selling knives to people under 18.
Home Office Minister Vernon Coaker has written to council chief executives and police chief constables asking them to recruit youngsters as “mystery shoppers” to check whether retailers ask for ID. The scheme will focus on 10 knife crime “hot spots”, including the West Midlands.
A Home Offices spokesman said: “Knife retailers in the 10 police force areas in England and Wales, that are the focus of the Government’s Tackling Knives Action Programme, will face ‘mystery shopper’ visits by underage children, under the supervision of police and Trading Standards officers.”
But figures uncovered by the Liberal Democrats showed only 71 people have been successfully prosecuted for selling knives to children in the last five years - and none of these jailed.
Fines were issued to 56 people, but 21 of these were for less than £200.
Ms Burt said: “This is a completely inadequate deterrent to unscrupulous shopkeepers who flout the law to sell these weapons to children and young people.
“These tiny fines and a lack of custodial punishment is the wrong signal to those who profit from the illegal sale of knives.”
She added: “It is too easy for children and young people to get hold of knives. Too many are being drawn into a culture of carrying and using knives.
“Liberal Democrats believe that the courts must take a much stronger stand against those who are fuelling knife crime by illegally selling knives to children and young people.
“Cutting the supply of knives will be one of the most effective ways to reducing knife crime in the first place.”
The maximum punishment for selling a knife to someone who is under age is six months in prison or a £5,000 fine. The age limit for buying a knife was raised from 16 to 18 last October.