Egypt's foreign ministry has called in the British ambassador to Cairo amid diplomatic tension after three Al Jazeera English journalists were sentenced to three years' prison each for reporting "false news".
John Casson made comments that were critical of the sentences, which the ministry said were "unacceptable interference" in the country's judiciary, and "incompatible with diplomatic norms and practices".
A court sentenced the Canadian Mohammed Fahmy, Australian Peter Greste and Egyptian Baher Mohammed on Saturday, sparking renewed uproar over the long-running case and highlighting the authorities' crackdown on free speech.
Fahmy and Mohammed were taken back into custody and Greste, who was deported to Australia, was sentenced in his absence. The three have previously spent 400 days in prison on terrorism charges.
Speaking to television cameras in Arabic after the verdict, Casson said he was "shocked and concerned by the sentences," in a case that is of "profound interest to Egyptians because it has become a symbol of the basis for stability in the new Egypt".
He said: "I am concerned that today's ruling will undermine confidence in the basis of Egypt's stability, both in Egypt and abroad."
The British Embassy said Casson met Hisham Seif al-Din, chief of staff to foreign minister Sameh Shoukry, at the ministry's request.
"Ambassador Casson explained the UK position on yesterday's court ruling set out in statements in London and Cairo yesterday", it said in a statement on Sunday, adding that Casson would transmit the Egyptian side's concerns to ministers in London.
The Foreign Office had no further comment.
Greste has said it would be "completely inappropriate" for the British Government to host talks with Egyptian president Abdel Fattah al-Sisi after the court's decision.
It was announced in June that there will be bilateral discussions later this year with the former head of Egypt's armed forces, who led the coup overthrowing Islamist president Mohammed Morsi.
But Greste, who was deported from Egypt in February, has said holding the talks would "send out a very negative message".
The case against the three embroiled their journalism in the wider conflict between Egypt and Qatar following the 2013 military ousting of Morsi.
The case began in December 2013 when Egyptian security forces raided the hotel suite used by Al Jazeera at the time to report from Egypt.
Authorities arrested the trio, later charging them with allegedly being part of Morsi's Muslim Brotherhood, which authorities have declared a terrorist organisation, and airing falsified footage intended to damage national security.
Since Morsi was ousted, Egypt has cracked down heavily on his supporters and the journalists were accused of being mouthpieces for the Brotherhood.
Al Jazeera and the journalists denied the allegations, saying they were simply reporting the news.
The three men were convicted on 23 June 2014, with Greste and Fahmy sentenced to seven years in prison and Mohammed to ten years.
The verdict brought international condemnation and calls for newly-elected Sisi to intervene.
Egypt's Court of Cassation, the country's highest appeals court, later ordered their retrial, saying the initial proceedings were marred by violations of their rights.
Two British journalists, Sue Turton and Dominic Kane, have previously been tried in their absence, and found guilty.
Turton has said it is dreadful news that Fahmy and Mohammed had gone back to prison, "and we will fight till our last breath to try to get them out".
Human rights lawyer Amal Clooney, who represented Fahmy on Saturday, said she and Canadian ambassador Troy Lulashnyk would be meeting Egyptian officials to press for a presidential pardon.
In an interview yesterday with the BBC, Clooney urged Sissi to issue a pardon "that would apply to all journalists, not just those who are foreign".
She said it was ironic that "the conviction was for tarnishing Egypt's reputation when the thing that the international community condemns Egypt for is this case and similar cases.
"This is what's tarnishing Egypt's image. I do think that he (Sisi) is aware of that and he has a way to fix it."