Judge says siblings of Nazma Ditta were motivated by religious and racial hatred and disapproval of her sexuality

Six siblings from a "traditional Asian Muslim family" in Lancashire have been jailed after attempting to kidnap the white girlfriend of one of their sisters, threatening to kill her because she had "messed with the wrong Muslims".

Sentencing them to between three-and-a-half and six years in prison, the judge said they had been motivated by religious and racial hatred as well as disapproval of their sister's sexuality.

"This case is about power and control," Judge Graham Knowles, QC, told the family at Preston crown court on Friday. "It's about striking terror into the heart, in order to control not just the body but also the will."

Almost three years ago Nazma Ditta, one of nine children from Blackburn, began a secret relationship with Sarah Harrison when both women worked at a clothes shop in Blackburn, Preston crown court heard.

Unhappy that Nazma, now 28, was in a same sex relationship – and with a white non-Muslim woman – six of Nazma's siblings plotted to break up the relationship. They claimed a teacher at a mosque had told them to "take action now or it might be too late" and had given permission "to be violent", the court heard.

The family wanted Nazma to enter into an arranged marriage with a cousin or another man, and discussed putting her on a plane to Pakistan, the judge noted. They concocted the plot via the online text messaging service WhatsApp, referring to it as "our mission as a family".

Three of Nazma's sisters, one wearing a full face veil, were caught on CCTV kicking and punching Harrison, 35, after she finished work at USC Clothing in Blackburn town centre on 20 June last year.

They were shown dragging her to the floor by her hair and snatching her handbag, before rifling through it to take out Nazma's passport and other things belonging to her. Beforehand, text messages exchanged between the siblings referred to "battering that bitch". One, sent by Nayyar Mehmood, 36, the second oldest sibling, urged her siblings to attack Harrison and warned them: "A kaffir [non-believer] is taking over." Another message referred to Harrison as a "honkey", offensive slang for a white person.

CCTV shown to the court showed sisters Nighat Morris, 39, the eldest child in the family, along with Atfah Ditta, 32, and Ghazala Ditta, 31, trying and failing to bundle Harrison into the back of a car before driving away. All three were sentenced to five years and four months after pleading guilty to conspiracy to commit actual bodily harm, attempted kidnap and robbery.

They were guarded during the attack by Tahmoor Ditta, 26, one of Nazma's brothers. He had a bradawl "clenched in his fist with the spike poking out between his fingers" which he used to try to scare off one of Harrisons's colleagues, who tried to intervene in the attack. He received a six-year sentence for conspiracy to commit actual bodily harm, attempted kidnap, robbery, possession of an offensive weapon and battery.

Both Harrison and her colleague told police Ghazala shouted: "Get her in, get her in, you've messed with the wrong Muslims, we're going to kill you."

Two other sisters, Nayyar Mehmood, 38, and Tosif Ditta, 35, received three-and-a-half years after pleading guilty to conspiracy to commit actual bodily harm.

All were ordered not to go near Nazma or Harrison, who are still a couple, until the judge discharges the restraining order.

The court heard Harrison has had to quit her job and sell her home for fear of reprisals. In a witness impact statement read to the court she said she was terrified that she would be the victim of an acid attack.

Nazma kept her sexuality a secret until 19 June last year, shortly after she moved out of the family home. "Knowing that the family would react very badly to the news that she was gay and that she was in an on-going relationship, Nazma Ditta had been slowly moving her belongings from the family home over to Miss Harrison's home in Blackpool since December 2012," said prosecuting barrister Richard Haworth.

"The family had a traditional arranged marriage planned for her and had already suggested a suitor – her cousin, to whom the family believed she was betrothed, and whom she in fact had already rejected," said Haworth. "In April 2013 three further suitors were suggested to her and a date of February 2014 was mentioned for her marriage and that of her two siblings, including Tasawar [a brother, aged 29], who the family are aware is gay." The Dittas were a "traditional Asian Muslim family", he added.

Nazma agreed to a marriage but resolved to run away and live with Harrison, the court heard. On 10 June she called Tasawar from a withheld number, telling him she was gay but not mentioning her relationship with Harrison. On 11 June Nazma had an "emotional"meeting with Tasawar, Ghazala and their mother, Rani, who was originally charged as part of the conspiracy to kidnap Harrison. (The charges against Rani were dropped earlier this year when the prosecution agreed not to submit any evidence in relation to her if six of her children pleaded guilty.)

After that meeting the family "closed ranks and told or cajoled and emotionally blackmailed" Nazma, said Haworth. She received abusive text messages from her siblings. One, from Tasawar, said: "I am dead to you, Delete my number. I hope you are happy with Sarah." One of her sisters, 31-year-old Ghazala, then texted to call Nazma a "selfish stupid bitch. Just wait until we get hold of you."

The defendants' barristers argued that the family was not as strictly religious or intolerant as the prosecution claimed. In mitigation, Nighat Morris's. barrister, Anthony Stephenson, said that while she accepted her part in the attack, she was not motivated by religious hatred or homophobia.

Her husband, a white man called Stuart Morris, was called to give evidence on Friday, and claimed that the Dittas welcomed him into their family. "Race, religion, sexuality has never been an issue in this family," he told the court, saying that not only was one of the sons – Tasawar, gay, but that one of the other daughters had been in a lesbian relationship while at university.

The siblings on trial claim they acted because they we had "genuine, deep seated concern as to Nazma's welfare," and "acting out of concern for their parents", said Ricky Holland, defending Aftah Ditta, 32, a university educated mother of two young children, who pleaded guilty to conspiracy to commit actual bodily harm.

Holland told the court: "there was a clash of cultural and personal beliefs in the end saw matters get desperately out of hand and I would submit that not one of them really gave any proper considered thought as to what they were embarking on, the enormity and frankly the nature of it."

But the judge didn't believe them, telling them he was not convinced that any claimed remorse was genuine.

After the sentencing, gay rights activist Peter Tatchell said: "We regularly get reports from lesbian and gay muslim people who say they have been threatened, intimidated or beaten up by family members who disapprove of their sexuality.

"It is a minority problem but it is very worrying that the victims are so fearful that they don't seek prosecution.

"It would be really helpful if muslim organisations and mosques spoke out and spoke out more frequently against all honour based violence, including that which targets lesbian, gay and transgender muslims."

Tehmina Kazi, director of British Muslims for Secular Democracy, said: "There is definitely an issue particularly of gay and lesbian [muslims/people] being forced into marriage. "It is usually emotional blackmail rather than physical force.The way to tackle this is two pronged – firstly we need the criminalisation of forced marriage to go through. We also need more awareness campaigns from the mainstream Muslim organisations."

A spokeswoman for the Muslim Council of Great Britain said: "We stand firm against all forms of discrimination, and this has been stated time and again. Any criminal activity is condemned outright as well. To suggest we are somehow 'silent' on this matter is ludicrous. Our statement on the issue of Muslim patrols was unequivocal. We will not, however, be commenting on each individual case as it happens. We must act within the rule of law and never promote or carry out any active hatred."

• This article was amended on 27 January 2014. The original version misspelt Nazma Ditta's surname in the subheading.