The Cypriot government said it had “full confidence” in its courts after the UK Foreign Office expressed “serious concern” over the fairness of a trial in which a British teenager was found guilty of lying about being gang raped by a group of Israeli men.

As condemnation of the decision mounts, the administration attempted on Tuesday to distance itself from the affair, insisting it was unable to intervene in cases heard before an independent judicial system.

“The government has full confidence in the judiciary and the courts of the Republic of Cyprus, which should be strictly left to enforce the laws of the state and to administer justice,” said its spokesman, Kyriakos Kousios.

Citing the EU member’s constitutionally regulated separation of powers, he added that the government did not comment on positions or allegations raised in matters before the courts.

Monday’s ruling was met with protests outside the district court in Famagusta, where female activists lambasted the proceedings as a miscarriage of justice.

In an unusual move, the UK Foreign Office said London would be raising the “deeply distressing case” with authorities in Nicosia.

Elucidating on his judgment before a packed court in Paralimni, the town closest to Ayia Napa, where the incident allegedly took place, Judge Michalis Papathanasiou said the Briton had been motivated by feelings of anger and shame after discovering that some of the Israelis had used their mobile phones to record her having consensual sex in a hotel room with one of the group.

“Her guilt is proven beyond reasonable doubt,” he said, emphasising that the teenager had voluntarily elected to revoke the fabricated rape claim.

After the retraction her alleged assailants, aged 15 to 22, were released from custody and allowed to fly home.

The Briton has insisted the alleged confession was forcibly extracted from her during eight hours of interrogation conducted without a lawyer or translator. “One moment I was a victim, the next, I was the accused,” she told the Sun newspaper. “Eight hours of interrogation, denied access to a lawyer, while those accused of raping me had legal representation immediately.”

With sentencing set for 7 January, anger over the verdict shows little sign of waning.

“Our society is polarised but for those of us who will go on protesting our starting point is that we believe the girl,” said Argentoula Ioannou, who was among those who recently set up the campaign group Network Against Violence Against Women (NAVAW). “As a lawyer with 30 years of experience I know that it is common practice for criminal complaints to be drafted or retracted by police,” she said. “They sit in stations, write statements and get people to sign them.”

Like other campaigners, Ioannou echoed the increasingly prevalent view that politics was also involved in a case in which Israeli diplomats and lawyers rallied to the defence of the alleged assailants within hours. “We can’t prove it, but there is this widespread sense that the girl has fallen victim to a political game of interests,” she said.

With the energy-rich waters of the eastern Mediterranean becoming ever more strategically important, Cyprus, like Greece, has worked hard in recent years to boost relations with Israel. The alliance is seen as increasingly significant at a time of growing Turkish belligerence in the region.

Campaigners have pointed out that on 28 July, the night the Briton reportedly revoked her rape claim, the Greek foreign minister, Nikos Dendias, was in Israel meeting the country’s political leadership. “I must say that the briefing here on everything that is happening in Cyprus is very important to us,” Dendias told reporters at a press conference in Jerusalem.

The offence of public mischief carries punishment of up to a year in prison and a fine in excess of €1,000 (£846). But the Briton’s lawyers have already announced they will be seeking recourse before the country’s supreme court, and if necessary, the European court of human rights once sentencing is handed down.

For critics, either move would highlight what is being seen as a culture of impunity surrounding victims of sexual offences in Cyprus.

“I don’t want to sound conspiratorial,” said one EU diplomat, “but there is something fundamentally wrong about this case when 12 young men are let go, no questions asked, and a young woman is treated like this.”

Nicoletta Charalambidou, the human rights lawyer heading the Briton’s legal team on the island, said her client’s ordeal highlighted the travails women so often faced when reporting incidents of violence.

“It would have been much easier at the end of the day if she had remained silent rather than enduring a six-month trial in Cyprus and having to stay with restrictive measures in this country just to prove that she is innocent and to try to prove that she was raped.”

Amid mounting criticism of his own failure to terminate the prosecution case, the island’s attorney general, Costas Clerides, said on Tuesday his intervention would have amounted “to nothing more than an obstacle to the establishment of the facts”.

“As the defendant has raised and continues to raise the matter of non-fair trial, this too is a purely legal and constitutional matter which must be raised and decided by the court,” he said in a statement that defended the court’s handling of the case.

Two of Clerides’s predecessors had argued that the case should be dismissed, fearing the international outcry it had triggered against Cyprus.