The sister of the murdered teenager Ben Kinsella fought back tears yesterday as she pleaded for teenagers to put down their weapons and realise the “pain and suffering” they caused.

Brooke Kinsella, 24, a former EastEnders actress, read a statement about the death of her 16-year-old brother, who was stabbed at 2am on Sunday after a bar fight spilt on to a North London street. He was the 17th teenager to die violently in the capital this year.

“My family are determined to fight in his memory to make the streets safer for our children,” she said. “Please, boys and girls, put down your knives and weapons and think about the pain and suffering they will cause. Parents, please talk to your children and encourage them to stop all this violence.”

Her parents and two younger sisters wept beside Ms Kinsella as she spoke. The actress, who played Kelly Taylor in the BBC soap, added: “Our hearts go out to every family who has also suffered this awful tragedy and now is truly the time to stand up and put an end to this.

“Please, please let us learn from Ben and every other child that has been stolen from us. We always knew that Ben would make a special mark in this world and although this is in the worst possible circumstances, hopefully he will be the one that finally puts an end to this.”

A post-mortem examination yesterday found that Ben had suffered numerous stab wounds.

He had gone for drinks with friends at Shillibeers bar in Islington, a week after finishing his GCSEs. An argument between two groups of youths erupted in the bar and continued in the street. Police believe that Ben was stabbed by four black teenagers, thought to be one or two years older, about 50 yards from the bar.

Police raided an address at a nearby estate yesterday and were scouring the streets near the bar to see if the stabbing had been caught on CCTV.

Detectives said that how events had unfolded was unclear but Ben's friends said that he had gone to help people he had known.

The murder happened in the middle of Operation Blunt 2, a high-profile Met initiative to fight knife crime.

Shortly before he collapsed, Benphoned a friend, saying: “Help me, help me.” Up to 50 people may have seen the attack but few have come forward. Senior officers are worried that witnesses are scared that their identities will not be protected after the publicity surrounding a recent law lords ruling.

Detective Superintendent Vic Rae, of the Metropolitan Police's Homicide and Serious Crime Command, who is leading the inquiry, said that police could still offer witnesses levels of protection and confidentiality.

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