An Islington shopkeeper ended up in court with a £400 bill after allowing a kitchen knife to be sold to a teenage boy.

But the town hall, which is ploughing cash into reducing knife crime, called the fine and costs award “disappointingly low”.

Paradise Pound Plus Ltd in Holloway Road admitted selling the 8cm paring knife – normally used for tasks such as peeling vegetables – to a 17-year-old sent in by an Islington Council sting operation.

The firm was fined £150 at Highbury Corner Magistrates Court on Thursday last week, and ordered to pay a victim surcharge of £25 and council costs of £235.

The teenager, who was a volunteer working with the council’s trading standards team, bought the knife on June 16. It was on open display in the shop, the council said, despite advice to shopkeepers from the council and police to lock blades away behind the counter.

The “Cook and Eat” brand knife was of the same brand and type as two used in a vicious attack in June 2014 that left a man with life-threatening wounds. Both knives had been bought from City Supermarket in Goswell Road by a 17-year-old.

Cllr Paul Convery, Islington Council’s community safety boss, described the sale of such knives to the under-aged as “unacceptable”.

“We have seen before how an under-age knife sale can lead directly to a violent crime,” he said, “and we will take action against businesses that ignore the law.

“We will also push for strong sentences against shops that do make under-age sales. In this case, the fine and costs awarded were disappointingly low.”

When contact by the Gazette, the shop manager said knives were now stored securely behind the counter.

The council today urged traders who want help and advice on how to avoid selling knives to children to visit islington.gov.uk/tradingstandards or email trading.standards@islington.gov.uk