William Hague has condemned Egypt's authorities for a lethal crackdown on protesters that has left hundreds of people dead.
The Foreign Secretary told his opposite number the "disproportionate use of force" was not acceptable and called for an end to the fighting.
But a Conservative MP urged him to "stop reading from the Foreign Office's script" and said the United States and Britain had been "too blind to see" the damage caused by the military coup.
In a call with Egyptian foreign minister Nabil Fahmy, Hague said Britain condemned all acts of violence, whether by the military or by some demonstrators protesting at the overthrow of former president of Mohammed Morsi.
He said that attacks on mosques and churches were "unacceptable" and called for places of worship to be protected.
Security forces stormed the al-Fath mosque in Cairo, while Muslim Brotherhood supporters have been blamed for a series of attacks on Coptic Christian churches.
"The Foreign Secretary emphasised UK condemnation of all acts of violence, whether disproportionate use of force by the security forces or violent actions by some demonstrators," a Foreign Office spokesman said.
"They also discussed the recent attacks on places of worship and the Foreign Secretary stressed that attacks on mosques and churches were unacceptable and that places of worship must be protected."
Hague urged the Egyptian government to return to the political road map published last month based on dialogue between parties who accepted peaceful political processes.
"He underlined the need for urgent steps by all sides to end the violence and enable a return to dialogue.
The Foreign Secretary also emphasised the EU's collective determination to support a peaceful resolution of the situation," the spokesman said.
Writing in the Mail on Sunday, Tory MP Douglas Carswell said the coup had undone what had been achieved in Egypt's democratic elections.
He wrote: "Why were so many in London and Washington too blind to see it?
"Partly, it’s because under President Obama, US foreign policy is bereft of either principle or higher purpose. Washington cannot even bring itself to call a coup a coup.
"In Britain, foreign policy-makers – perhaps too deferential to Washington – have failed because they still seem to believe that diplomacy is a conversation between the world’s elites. In the age of Twitter, there are millions of others involved.
"Come on, William Hague. Stop reading from the Foreign Office’s script and start to speak up for democracy in every language – especially Arabic."Suggest a correction