Alesha Ahmed sobs as she tells court how her 17-year-old sister gasped for air as their parents suffocated her

Shafilea Ahmed's mother said in Urdu: "Just finish it here", before she and Shafilea's father jointly suffocated their daughter to death in front of their other children, a court was told on Wednesday.

Shafilea's younger sister, Alesha Ahmed, 23, told how on 11 September 2003 her mother, Farzana, had pushed Shafilea, 17, on to a settee at their home in Warrington, Cheshire, with both hands, after previously arguing with her about her choice of clothing and boyfriends. All four siblings witnessed the attack, she said.

Alesha, who gave evidence at Chester crown court from behind a screen, sobbed as she said: "They both started hitting her. She was scared as usual.

"I can't remember which one grabbed a bag, just a plastic bag, which they put in her mouth and put their hands over her – both of them." Alesha said her sister was lying on the settee.

Her father held Shafilea down "with his legs" and she kicked her legs in protest. Alesha said she could see Shafilea's eyes open really wide "and she was just gasping for air. She wet herself because she was struggling so much".

Then she stopped struggling. "That was it, as if she was gone," she said, sobbing audibly in the otherwise hushed courtroom. Her parents kept their hands on her mouth "even when she'd stopped struggling" for 15-30 seconds.

Previously she told how her mother was "not happy" about her sister's choice of western clothing that night – she was wearing a T-shirt and white stretchy trousers. Her parents, Iftikhar Ahmed, 52, and Farzana, 49, deny murder.

Alesha described being frozen in shock. "My father pulled her off the settee and put her on the floor in quite a harsh way. I remember shortly afterwards he punched her in the chest for no reason." He reached for some keys to the shed and garage and she left the room.

Her sister was not moving but her eyes were open. The court has heard Shafilea was subjected to a campaign of domestic abuse after she refused to conform to her parents' wishes. She drank bleach in Pakistan and ran away from home.

After her death, when Alesha was upstairs with her siblings, her two sisters were upset but her then 13-year-old brother was not. He told her "she deserved it".

Returning down the stairs, she saw her mother with printed flowery sheets in the kitchen, binbags and rolls of black and brown tape. She looked through curtains and saw her father on the driveway with an object wrapped in black plastic binbags and tape. "The way it was it just looked like my sister Shafilea." She heard a car drive off and a few hours later she heard it return.

Her mother slept that night in Shafilea's bed in the room she shared with her sister while Alesha pretended to be asleep.

The next morning her father took her to school. Her mother later told her if anyone asked she should say her sister "had just run away as usual". But she and her brother were overheard by a teacher "talking about the fact that my parents had just killed my sister".

Shortly before lunch, she began crying and ran to the school's toilets followed by a group of friends. They asked what was up "and I just blurted out that my dad had killed my sister. I remember saying he'd cut her up but I don't know why.

"The school bell went and I told them not to say anything. I just needed to tell someone. I didn't want anyone else to know because I would be in trouble".

When questioned by her form teacher, she denied saying it. Another teacher asked where Shafilea was and Alesha said she had run away from school again.

After school she and a group of friends drank alcohol in a park. Alesha, who had never previously drunk alcohol, had two cups.

"It seemed everyone knew about it and they were talking, whispering about it, saying Shafilea was in a pothole or buried in the back garden.

"They were staring at me. It was not good at all because I trusted my friends and I was fearful of it escalating and people telling everyone. I was just very scared."

When the police arrived and asked to speak to her alone, she denied saying Shafilea was dead. Later that year, when her parents were arrested on suspicion of kidnap, the children were interviewed. She told them Shafilea had run away.

In February 2004, the police told her parents a body had been found, but Alesha found out from a news report, as they did not tell their children.

Asked if her parents had seemed upset following Shafilea's disappearance, she appeared to laugh and replied: "No."

On another occasion, they were visiting a family friend, Tariq, in Rawtenstall, Lancashire, and everybody went out, leaving them in the room.

"He looked at me and said: 'They did it, didn't they?' I said yes and broke down. Shortly after, the rest of the family started to arrive and he told me to clean up my face. I never spoke to him about it again."

The trial continues.