A teenage girl has been stabbed to death during a clash with a female gang.

Sian Simpson, 17, who wanted to become an accountant, was killed by a single blow from a kitchen knife during a fight in Croydon, South London.

The argument is believed to have centred on the claim that a man had fathered children with two of the women.

Witnesses said that the student had been trying to defend a cousin from an attack by another girl when she was stabbed in the middle of the street on Tuesday evening.

A gang of almost 20 girls aged between 13 and 20 had been at the scene when Miss Simpson arrived to support Chantal Campbell during an argument about a former boyfriend.

Miss Campbell, who has a three-month-old son, Demariuse, with Nathan Davidson, is believed to have argued with a woman aged 18 who claims that she is pregnant by the same man.

Last night the heavily pregnant woman and a friend, also 18, were being questioned by police after being arrested on suspicion of murder. For legal reasons, neither of the women can be named.

The death comes after the release of Home Office figures that show that the number of women charged with violent offences has almost doubled in the past decade. In all, 9,397 were charged in 2006.

A meeting of senior police officers and community leaders took place in Croydon yesterday afternoon and extra patrols were deployed in the area.

Miss Simpson’s father, Joseph, 41, said last night: “It is just so stupid what has happened. I can’t believe people do these sort of things now.

“In my day there was trouble and fights but I don’t remember girls killing girls. They pick these things up from TV. They have no morals and because they are young, no fear. They have no regard for life.

“She was a good kid. She was bubbly, bright and she was beautiful.”

Cassie Webb, 16, a friend of the dead teenager, said: “This girl threatened to kill Sian’s cousin’s baby. Sian was so loving and open she would not have hurt anybody.”

Annie Naine, 49, whose flat overlooks the scene of the murder on the outskirts of Croydon town centre, said: “We heard screaming and shouting coming from the road.

“I went to the balcony and saw a big group of teenage girls rowing. It went on for about 20 minutes and there were insults flying.

“I heard one girl say, ‘I know who the father of my baby is — what about you?’ Suddenly the row boiled over and punches were thrown. Two girls were pulling each other’s hair. It was raining heavily and there was thunder and lightning but you could clearly hear the screams.

“The black girl tried to walk away but her legs buckled and she collapsed in the road. She was wearing a white top but very quickly it turned red with blood and there was blood coming out of her mouth. It was horrific.”

Another witness, who asked not to be named, said: “There was a lot of screaming between the girls . . . Then I heard someone say, ‘She’s been stabbed, she’s been stabbed’, and a lot of the girls ran away.

“The knife was still there lying in the middle of the street.”

Dozens of people saw the attack, which happened close to a fun day that had been organised by the South London Family Housing Association.

Miss Simpson’s aunt, Cheryl Simpson, said that the dead girl had studied at Carshalton College after taking her GCSEs at Haling Manor High School, Croydon.

Mrs Simpson said: “Sian got a call from Chantal saying she needed help so she got into a cab to go to her. She went to help her friend and she was met by an ambush.”

Miss Simpson lived with her maternal grandmother and had one brother and three sisters. Her father, a self-employed courier, is separated from her mother, Julie.

Her aunt said: “She wanted to be an accountant or to work with children.”

A Scotland Yard spokesman said that two women in their late teens had been arrested and were being held at separate police stations.

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