Al-Jazeera English's managing director Al Anstey said the sentencing of the journalists defied any "logic, sense, and any semblance of justice".
He said the only sensible outcome now was for the sentences to be overturned.
Today three colleagues and friends were sentenced, and will continue to be kept behind bars for doing a brilliant job of being great journalists.
Guilty' of covering stories with great skill and integrity. 'Guilty' of defending people's right to know what is going on in their world.
Peter, Mohamed, and Baher and six of our other colleagues were sentenced despite the fact that not a shred of evidence was found to support the extraordinary and false charges against them. At no point during the long drawn out 'trial' did the absurd allegations stand up to scrutiny.
There is only one sensible outcome now - for the verdict to be overturned, and justice to be recognised by Egypt.
Downing Street said the Prime Minister was "completely appalled" by the verdicts, and Egypt's ambassador has been summoned to the Foreign Office, the Foreign Secretary said.