Theresa May UK home office
© Suzanne Plunkett/ReutersHome secretary Theresa May can strip dual nationals of their British citizenship if it is "conducive to the public good".
Home Office refuses to explain why use of law introduced following London bombings has increased

Increasing numbers of British nationals are being stripped of their citizenship under Home Office powers introduced in the wake of the 2005 London bombings.

The number of people subject to the power, under which the home secretary can deprive dual nationals of their British citizenship if it is deemed to be in the public interest, has increased since the coalition government came to power.

The measure was included in the 2006 Immigration, Asylum and Nationality Act as a direct result of the July 2005 bombings in which 52 people died and more than 700 were injured. It was used only four times in the following four years, but has been used nine times since last year's general election.

Five of the dual nationals deprived of their citizenship were British Pakistanis, while two were of dual British and Sudanese nationality. The remaining six were Australian, Iraqi, Russian, Egyptian and Lebanese dual nationals.

To date 10 of the orders have been appealed against.

The figures were obtained by the Guardian under the Freedom of Information Act after the Home Office refused to release them. It also refused to offer any explanation for the increase, saying: "British nationality is a privilege and the home secretary has the ability to remove it from dual nationals when she believes it to be in the public good."

Under the terms of the act the home secretary can deprive an individual of British citizenship if she believes it to be "conducive to the public good", a test historically applied to non-Britons facing deportation.

Previously home secretaries could act only if the British citizenship of a dual national was said to be "seriously prejudicial to the vital interests of the UK", usually because individuals were spies. Immigration lawyers and some MPs have criticised the power, saying the public interest test is set too low. Some are also concerned that British citizenship can be stripped from individuals whose other nationality is meaningless to them.

At least one of those who have lost their British citizenship is understood to have been born in the UK, while others are thought to have lived in Britain since infancy.

The Australian who lost his British dual nationality is David Hicks, who spent more than five years as a prisoner at Guantánamo Bay after being detained in northern Afghanistan after the 9/11 attacks. The Russian is Anna Chapman, the spy deported with nine others from the US last year. She acquired British nationality through marriage before travelling to the US to join a network of sleeper agents.

The Home Office refused to explain the reasons for depriving the remaining 11 dual nationals of their British citizenship, maintaining it still has responsibilities to them under the Data Protection Act, although officials briefed journalists about Chapman's case.