Shopkeepers who sell knives to children under 16 are being handed "pitiful" fines rather prison terms, the Liberal Democrats said on Wednesday, as it emerged no one was jailed for the offence in the five years to 2006.

Despite rising numbers of teenage knife deaths the most stringent penalties are not being imposed in England and Wales, the opposition party said.

None of the 71 people convicted of selling knives to under 16s between 2002 and 2006 were jailed, despite the maximum sentence available being six months.

One offender was given a community sentence, but most offenders were fined less than 500 pounds - well short of the maximum 5,000 pounds.

The figures were published by the Liberal Democrats following parliamentary questions.

"Unscrupulous shopkeepers who sell knives to kids are profiting from the violence on our streets," Liberal Democrat Shadow Home Secretary Chris Huhne said in a statement.

"It is unacceptable that so few of them are being punished and those that do are being given such pitiful fines.

"If we are to tackle knife crime, a strong message must be sent to those who ply this deadly trade.

"Fining them a few hundred quid is not going to do that."

Sixteen teenagers have died from fatal stab wounds in London so far this year.

The ban on selling knives was extended to under-18s last year, but figures are not available for these yet.

Mayor of London Boris Johnson has pledged to make combating knife crime one of his top priorities, promising more hand-held scanners and police powers to stop and search by consent.

The Liberal Democrats this month launched its proposals to tackle youth crime, including intelligence-led stop and search and "hot spot policing" targeting knife as well as gun crime.

Council trading standards officers carry out test purchases and bring to court anyone found selling to under-age youngsters.