The fate of Hosni Mubarak must be decided in a "transparent and impartial" way, William Hague said amid fears the former Egyptian president's release from jail could further inflame unrest.
The comments came amid concern the decision of an Egyptian court to order the release on bail of Mubarak - detained since he was ousted by a pro-democracy rising in 2011 - could worsen tensions.
"This is a matter for the Egyptian judicial system but we hope that all the decisions they take, particularly on such a sensitive matter, will be transparent and will be impartial," Mr Hague said.
More top news
Rain in the north tonight, cloudy and humid in the south
In an exclusive interview with ITV News, 100 metre world champion Justin Gatlin also said that booing at the World Championships "did hurt".
The 26-year-old had just given birth to her third child and was being transferred to a different floor when the tragedy happened.