The United Arab Emirates has charged a British PhD student with spying in the Gulf country, as his wife Tuesday called on Britain to defend his innocence.

Matthew Hedges stands accused of “spying for a foreign country, jeopardising the military, political and economic security of the state”, UAE attorney general Hamad al-Shamsi said late on Monday.

The 31-year-old, who was researching the UAE's foreign and internal security policies after the 2011 Arab Spring revolutions, was detained at Dubai airport on May 5.

Hedges' wife Daniela Tejada said Tuesday he been “held in an undisclosed location in the UAE in solitary confinement” with limited access to the consulate and his family as well as no access to a lawyer until last week.

She said Hedges had been told last week he “was being charged with gathering information and sharing it with a foreign agency - the UK Government”.

Tejada called on the British government to “clarify publicly that Matt is innocent of the charges and that there have been many falsehoods said about him”.

“This horrifying situation has been going on for far too long,” she said.

Britain's foreign office said it was supporting Hedges and his family and had been “in close contact with the local authorities”, a spokesperson said.

British Foreign Secretary Jeremy Hunt told AFP last week he was “very worried” about Hedges' fate.

“I've spoken to the Emirati foreign minister twice now on this matter face to face so they are very aware of our concerns and we are monitoring it very closely,” he said.

The charges against Hedges are based on evidence from investigations carried out by the public prosecution, according to the attorney general.

Hedges had been posing as a researcher to cover his activities, he said, adding that the accusations were backed by “information taken from his electronic devices”.

Tejada, who has visited her husband once and spoken to him on the phone several times, told AFP last week her husband “simply isn't guilty of anything”.

“He was just doing academic research,” she said, adding that his research involved only open source material.

“He's not disclosed anything... classified or confidential,” she said, adding that Hedges had lived in the UAE for “several years” before he returned to Britain in 2015.