Sayeeda Warsi, a senior minister in Britain's Foreign Office, resigned on Tuesday, accusing Prime Minister David Cameron's government of taking a morally indefensible approach to the conflict between Israel and Hamas.
While the British government has repeatedly called for an immediate ceasefire in Gaza, Cameron has come in for criticism from political opponents and some members of his own party for what they say has been his reluctance to condemn Israel's actions in stronger terms.
Warsi announced her decision as Israel pulled its ground forces out of the Gaza Strip and started a 72-hour ceasefire with Hamas mediated by Egypt as a first step towards negotiations on a more enduring end to the month-old war.
Gaza officials say the war has killed 1,865 Palestinians, most of them civilians. Israel says 64 of its soldiers and three civilians have been killed since fighting began on July 8, after a surge in Palestinian rocket launches.
Warsi's resignation is embarrassing for Cameron, who has been accused of filling his government with too many middle-class white males. Warsi was not a full cabinet member but had the right to attend and played an important role in mediating between the government and Britain's Muslim community.
Warsi, a baroness who sits in the upper house of parliament, in 2010 became Britain's first Muslim to serve in cabinet but was later demoted to be a senior minister of state at the Foreign Office and a minister for faith and communities.
She announced her resignation on Twitter, publishing a copy of a letter she sent Cameron with the reasons for her decision.
Our approach and language during the current crisis in Gaza is morally indefensible, is not in Britain's national interest and will have a long term detrimental impact on our reputation internationally and domestically, Warsi, 43, said.