British Foreign Secretary William Hague's comments came Wednesday during a phone call with Egyptian Vice President for Foreign Affairs Mohamed ElBaradei, shortly after the Egyptian cabinet extended an interior ministry policy aimed at curbing "acts of terrorism and road-blocking," Ahram Online reported.
The extended mandate was a warning to the Muslim Brotherhood to stop blocking roads, Ahram Online said.
During the phone call, Hague called for "the release of all political detainees, including President Morsi, unless there are criminal charges to be made against them."
Following his talk with ElBaradei, Hague released a statement saying it is important any charges against detainees are not politically motivated.
Hague also said the Egyptian security forces were responsible for the killing "of over 80 civilians last weekend."
"I made clear that the U.K. condemned this excessive use of force, along with the attacks against security forces in Sinai, Mansoura and elsewhere," Hague's statement said.
Meanwhile, Egypt's Tamarod rebel campaign, whose mass protests led to Morsi's ouster, compared the deposed president to Adolf Hitler.
At a meeting with German Foreign Minister Guido Westerwelle in Cairo Wednesday, rebels expressed outrage Germany wants Morsi released, Ahram Online reported Thursday.
"We told him we resented some of his statements where he asked for the return of the deposed president," rebel spokesman Mahmoud Badr wrote on his Facebook page after the meeting.
"We told him we're here to see him to tell him about the story of Hitler who came by his people's votes but turned against democracy. Why did you reject Hitler in Germany but want him back in Egypt?"
Westerwelle who arrived in Cairo Wednesday reportedly demanded Morsi's release, describing him as a political prisoner, the website said. The Egyptian interim government has yet to respond to the German foreign minister's request to meet with Morsi, the site said.