A British-born father and three of his sons, all accused of being Islamist extremists with ties to al-Qaeda, have been exiled by Theresa May because of the threat to national security.

They are believed to be the first British family to be collectively stripped of their citizenship since Mrs May took over in 2010 and the father said the decision was 'tearing our family apart'.

The father admitted his daughter had gone to fight in Syria with her husband, a known jihadist, but denied the terrorism allegations levelled at him.

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A British-born father (left with his two granddaughters and his fourth son) has been stripped of his British citizenship because of the threat to national security. Right: One of his exiled sons, who is in his twenties

The 51-year-old father from Newcastle had his citizenship revoked, along with his three sons aged in their twenties, under the British Nationality Act 1981 while they were in Pakistan.

His wife and their fourth son, a disabled teenager, have not been exiled but could not return to Britain because they wanted to remain with the rest of the family.

'We are innocent of all the allegations but our situation prevents us from answering the allegations,' the 51-year-old told the Sunday Times.

'We are British through and through. The best of British values don't contradict Islamic values. To this day, English is the only language we speak.

Home secretary Theresa May has exiled a British-born father and three of his sons all accused of being Islamist extremists

'We as a family have been abandoned by the British [government] and this is tearing our family apart.'

He denied 'ridiculous' claims that he was linked to both al-Qaeda and Pakistan-based Lashkar-e-Taiba (LeT), saying that would be like being involved in the Conservative and the Labour party.

But he revealed that his daughter, 22, was now living in Syria with her three children and 'abusive husband' who was treated like a VIP by jihadists.

He said he saw a picture of his daughter, who still has British citizenship, posing with a heavy sub-machine gun.

The family will be appealing the decision after a legal attempt to reinstate their citizenship was thrown out by the Special Immigration Appeals Commission (SIAC).

They all have Pakistani passports, but said they feel like outsiders in the country and were desperate to 'return home'.

A spokeswoman from Liberty, the human rights body, said the family were victims of the UK's secret courts.

In his judgment, Mr Justice Mitting acknowledged the impact on the private and family life of the wife and youngest son who both remain British citizens.

But he said the move was 'justifiable' because of the 'threat to national security'.

Mrs May said her decision was based on an assessment by MI5, the security service and the claims that they were linked to terrorist groups.

A letter sent to the family in 2011 and signed by the Home Secretary said their citizenship would be revoked because 'it would be conducive to the public good'.

The father denied claims that he was linked to both al-Qaeda (pictured) and Pakistan-based Lashkar-e-Taiba

A British-born family have been stripped on their citizenship for alleged links to terrorism, amid claims they are the victims of the UK's secret courts, pictured is the Royal Courts of Justice

'My decision has been taken in part reliance on information which, in my opinion, should not be made public in the interests of national security and because disclosure would be contrary to the public interest,' the letter adds.

A spokeswoman for the Home Office said: 'We cannot comment on individual cases.