The former Adelaide man, who has been held at the US base in Cuba for more than four years, is entitled to a UK passport because he has a British mother.
However the Home Office is resisting a High Court order to grant him British citizenship on the basis of his alleged involvement with the Taliban in Afghanistan.
Unlike Australia, Britain is opposed to the military tribunals planned for the detainees at the Guantanamo Bay detention facility and has successfully lobbied to have its citizens released from the camp.