A Briton jailed for life for spying in the United Arab Emirates (UAE) pleaded guilty when he was confronted with "compelling" evidence, prosecutors say.
Matthew Hedges, 31, always said he was innocent and had been researching the country's security strategy for a PhD.
The verdict angered the UK government, triggering a diplomatic row with the UAE, a long standing ally.
Foreign Secretary Jeremy Hunt urgently wants a "call with Foreign Minister Abdullah bin Zayed".
He feels personally "betrayed" by the verdict as he was given assurances only nine days ago in a meeting with the Emirates' Crown Prince that this would not be the outcome of the case, the BBC's James Robbins said.
Mr Hunt has pledged to meet Durham University student Hedges' wife Daniela Tejada on Thursday.
He also said he had raised the case with the "highest levels of the UAE government", adding the verdict was "not what we expect from a friend and trusted partner of the United Kingdom, and runs contrary to earlier assurances".
But in a statement, UAE Attorney General Dr Hamad Saif Al Shamsi, said Hedges had pleaded guilty to all charges after the court presented him with "compelling legal evidence concluded after thorough judicial investigations".
''The defendant confessed in detail to his crimes during investigations whereby he was accorded his full rights and assurances as per the UAE Constitution and state laws to fair and transparent trial,'' he said.
Dr Al Shamsi also said Hedges was in court with representatives from the British Embassy and he "exhausted all methods of defence by his lawyer during the trial".
Hedges' family however, said that during the first six weeks of his detention he was interrogated without a lawyer and consular access was unavailable.
During this time he was made to sign a document in Arabic which transpired to be a confession, they said.
"Matthew does not speak or read Arabic," the family added.
Ms Tejada said her husband shook his head as the verdict was delivered, adding: "I am very scared for Matt.
"Matthew is innocent. The Foreign Office know this and have made it clear to the UAE authorities that Matthew is not a spy for them."
She said the British government "must take a stand now" and the UAE authorities "should feel ashamed for such an obvious injustice".
At prime minister's questions, Tory MP Crispin Blunt told Mrs May she should make clear to the UAE that "if he is not released, I don't see why we should be committed to their defence".
According to Abu Dhabi newspaper The National, a life sentence means a maximum of 25 years in jail, after which Hedges would be deported.
Hedges, who is also liable for the costs of the case, has 30 days to appeal during which time he will be held in custody, the paper reports.
Hedges is said to be in a poor state of mental health, the BBC understands, and Ms Tejada has previously criticised the lack of treatment he has received in prison.
Vice-Chancellor of Durham University, Professor Stuart Corbridge, said the conditions Hedges was being held in "breached his human rights".
"[And] this judgement has been delivered in the absence of anything resembling due process or a fair trial," he said.
"There has been no information given on what basis Matt was handed this sentence and no reason to believe that Matt was conducting anything other than legitimate academic research."
What are the links between the UK and UAE?
By BBC Reality Check
More than 5,000 UK companies do business in the UAE - it's the UK's largest export market in the Middle East and the 13th biggest in the world.
The UK exported a total of £9.8bn of goods and services in 2016.
The top UK goods exported to the UAE last year were:
- machinery and mechanical appliances
- electrical equipment
- precious stones and metals
- motor vehicles
- optical, photographic and medical equipment
The UK imported £4.8bn worth of goods and services from the UAE in 2016.
There are about 120,000 UK nationals living in the UAE, according to the UK government.
British educational institutions have a presence too, with 11 UK universities represented.
The UK also has important military ties with the UAE and in 2012 announced a defence partnership with the country.
Last year a BBC investigation uncovered sales of surveillance equipment between a UK company and countries in the region, including the UAE.