Westminster killer Khalid Masood’s teenage daughter defied his orders to wear a burqa — and headed to a school prom night in a ­revealing backless dress.

Unlike her older sister, student Teegan Harvey, 18, refused to bow to pressure from fanatical Masood and convert to Islam.

Family friends said radicalized Muslim covert Masood, who killed four people and wounded more than 50 during an 82-second rampage in Westminster last week, demanded both his daughters become Muslims and don the veil.

Older sister Andi, now 24, converted to Islam six years ago and left her mum, Jane Harvey, and sister, Teegan, behind at their home in Tunbridge Wells, Kent, to move in with her dad and his new partner in Luton, Bedfordshire, about 35 miles north of London.

They later moved to Birmingham, where Andi is said to have been persuaded by Masood to cover herself in a burqa.

She is also reported to have changed her name to an Arabic one.

But younger daughter Teegan resisted her father’s demands to give up her Western lifestyle.

The teenage beauty posed for the camera in a revealing backless dress at a prom night in May last year for soon-to-be graduates of Tunbridge Wells Girls’ Grammar School.

She had earlier come under pressure from her father to convert to Islam after she turned 16.

Her mother, Jane, managing director of a chemicals company, fought desperately to prevent her younger daughter from joining her father.

Luke Lawrence, 23, close friends with Andi at school when she lived in Northiam, East Sussex, with both her parents and sister, said: “Jane was totally against the idea and wanted Teegan to remain with her.

“But Andi was older and could be very headstrong, so she just went off and did it anyway.”

Luke said Andi was popular and attractive and he couldn’t understand why she had gone to live with her “nutter” dad.

Masood had changed his name from Adrian Elms after converting to Islam while in prison awaiting trial for an alleged knife attack in 2003.

Luke said: “Andi was a lovely girl, but when she moved away to become a Muslim, she cut off contact with her friends here.

“She went off to live with her dad after he converted her. I’m not sure why she went with him, he was a nutter.

“Teegan stayed with her mum.”

Before converting to Islam and moving in with her dad, in 2008 Andi had been involved in a serious accident outside her house, which opens onto a fast road on the outskirts of Northiam.

Luke said: “She stepped out of the house with headphones on, without looking, and got hit by a van.

“She was seriously hurt and was in a wheelchair for a while. It left her traumatized and she was never quite the same afterwards.”

Khalid Masood spent hours by his daughter’s bedside in the hospital, praying for her to recover from her injuries, in twisted contrast to what he did nine years later at Westminster Bridge.

Andi is still living in Birmingham, where one friend of mum Jane said: “She wears a full face veil and I think she has changed her name. It was her father who had helped convert her.

“He wanted the younger daughter to convert, but Jane was against it and there was quite a family struggle.

“I know Jane was very upset and wanted her to stay at home and continue her studies.”

Meanwhile, Jane and Teegan have been keeping a low profile at their home in Tunbridge Wells, trying to digest the shocking attack carried out by Masood.

Masood, who was born Adrian Elms, met Jane, his first partner, while working together in the late 1980s at Aaron Chemicals in Bodiam, East Sussex, which Jane now runs.

The couple moved to the sleepy village of Northiam, near Rye, and in 1992 had first daughter Andi Jay, before Teegan Adrienne followed six years later.

But Jane, now 48, had to put up with her partner’s rages.

She ended the relationship in 2000 when he was arrested and jailed for two years over a knife attack.

After his release, Masood moved 30 miles west to Eastbourne while Jane went back to her hometown of Tunbridge Wells.

He was later charged with attempted murder in 2003 but acquitted by a jury, having spent six months in lockup — where he became radicalized.