Matthew Hedges, the British academic held in the United Arab Emirates for six months on spying charges, has lodged a legal complaint against the Foreign Office (FCO) over allegations that it failed in its duty of care to negotiate his release and help him clear his name.

Hedges and his wife, Daniela Tejada, are demanding that his conviction be quashed and an independent inquiry be held into the case. If it is not, he says, they will sue the FCO.

It was a year ago this Sunday that the Durham University PhD candidate, who had been in the UAE to research his thesis, was arrested at Dubai airport as he left the country. He was accused of spying and went on to spend six months in solitary confinement in a windowless state security office, where he was regularly threatened with torture and interrogated for up to 15 hours a day.

In November last year, after a short hearing with no lawyer present, Hedges, 31, was sentenced to life in prison at an Abu Dhabi court. But in a remarkable turnaround just days later, he was officially pardoned and returned to the UK to be with Tejada, 27, who had campaigned tirelessly for his release.

The couple believe Hedges incarceration was prolonged by Britain’s close ties with the UAE and attempts to maintain friendly diplomatic relations.

Tejada said: “He is still a falsely convicted spy and after he was released on a pardon, everybody decided to pretend that nothing had happened. There was no sense of accountability or justice for all the months that Matt endured in solitary confinement.”

Hedges, the first western academic to be detained for spying in the UAE, revealed that following his release, some of his friends and acquaintances had been expelled from the country, while others have been interrogated.

He said: “People have been affected in a multitude of different entities. I don’t know why that has happened. Several people have been expelled from the country and other persons have been spoken to.

“And it isn’t just people I spoke to for my thesis. Some of these people are just Facebook contacts of mine – I didn’t even meet them on the trip. This is the personal safety of people who are completely unrelated to this issue and they are still seeing the consequences of what happened to me.”

When Hedges was first arrested, Tejada, who works in public relations, was advised by the FCO to maintain her silence despite wanting to go public about his confinement. However, after six months of alleged inaction and no signs of a release, Tejada went to the media and within weeks Hedges was back in the UK.

“The Foreign Office only took action after seven months because of public pressure,” she said. “We want there to be an independent inquiry into how Matt’s specific case was handled and for his conviction to be quashed. If legal action needs to be taken, then so be it, because they need to be held accountable.”

Hedges, who has been diagnosed with post-traumatic stress disorder after suffering nightmares and flashbacks and remains dependent on drugs that he was given during his confinement, said his life was still on hold.

He added: “That’s why we take so much insult in the Foreign Office’s response, because they think that just because a pardon was issued and I am out, everything is going back to normal, but it isn’t. I have PTSD, I am a falsely convicted spy, and friends, family and contacts are being harassed, not just in the UAE but beyond, just because they know me.

“I want to get my life back on track and speak to people freely but it is just not safe until my conviction is quashed.”

Hedges’ ordeal began on 5 May when he was detained while trying to leave the UAE after a two-week research visit to interview sources on its security structure after the Arab spring. Hedges says he was forced to confess “under duress” to allegations of spying for Britain, then sentenced to life in jail.

After international outrage over his treatment and an intervention from the foreign secretary, Jeremy Hunt, the UAE’s President Khalifa bin Zayed Al Nahyan eventually issued a pardon.

Hedges has always maintained his innocence. Alex Younger, the head of MI6, has said he was “perplexed” as to why Hedges was accused of espionage on behalf of the agency.

Hedges has previously spoken about the Emirati friend who reported him and said he does not feel any resentment towards him. He now believes the friend may also have been detained.

Hedges’ lawyer, Rodney Dixon, who has submitted a 16-page official complaint, said: “The FCO should be taking all possible steps to clear Matthew’s name, especially as he was wrongly convicted by the UAE of being an agent of the UK government. And yet they have flatly refused and left him in the lurch.

“Matthew went through an unimaginable ordeal in detention in the UAE, and is now having to fight for justice without the government’s help.”

In response, an FCO spokeswoman said its ministers and staff in the UK and the UAE had worked “incredibly hard” to support Hedges and his family during his detention and following his release.

She added: “Our staff maintained regular contact with Matthew and his family in the UK, updating them on developments in his case when we had information we could share, in compliance with our legal obligations under the Data Protection Act.”