A British minister who was the first Muslim to sit in the cabinet resigned on Tuesday over the government's "morally indefensible" policy on Gaza.
The decision by Baroness Sayeeda Warsi, a minister at the Foreign Office and for faith and communities, heaped fresh pressure on Prime Minister David Cameron to take a tougher line against Israel over its actions in Gaza.
His coalition government has faced sustained criticism in recent days, led by the main opposition Labour Party, that it has not spoken out strongly enough over a conflict that has killed 1,867 Palestinians and 67 people on the Israeli side.
"Our approach... 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 wrote to Cameron in her resignation letter.
She said there was "great unease" in the Foreign Office, where Philip Hammond took over as Foreign Secretary from William Hague last month, about how recent policy decisions had been made.
While Warsi's star has dimmed in recent years, she was once a high-profile example of Cameron's desire to diversify his Conservative party away from its traditional white, male base.
Warsi's parents were Pakistani immigrants and she trained as a lawyer before being made a member of parliament's upper House of Lords in 2007.
She was appointed to Cameron's cabinet when his coalition government took power in 2010 but was shuffled out of the full cabinet, the powerful inner circle of government ministers, in 2012.
Warsi describes herself on her website as "best known for being the first Muslim to serve in a British cabinet and the foremost Muslim politician in the Western world".
- 'Inexplicable' silence on Gaza -
Labour leader Ed Miliband last week accused Cameron of "inexplicable" silence over the suffering of Palestinian civilians in Gaza, now in a three-day ceasefire.
"The government needs to send a much clearer message to Israel that its actions in Gaza are unacceptable and unjustifiable," Miliband said.
"What I want to hear from David Cameron is that he believes that Israel's actions in Gaza are wrong and unjustified, and we haven't heard that from him."
On Monday, Cameron said the United Nations was "right" to condemn an air strike near a school in Rafah on Sunday which killed 10 people but would not say whether he thought it was a "criminal" act.
Downing Street said Cameron regretted Warsi's decision, and added: "Our policy has always been consistently clear -- the situation in Gaza is intolerable and we've urged both sides to agree to an immediate and unconditional ceasefire."
Finance minister George Osborne called her resignation "disappointing and frankly unnecessary".
"The British government is working with others in the world to bring peace to Gaza and we do now have a tentative ceasefire which we all hope will hold," he added.
Warsi's resignation drew praise on Twitter from some Labour MPs.
"Very courageous of my brave friend @SayeedaWarsi to resign over this Government's inexplicable silence and total weakness on the #Gaza crisis," wrote Sadiq Khan, Labour's lead spokesman on justice.
Meanwhile, London Mayor Boris Johnson, seen as a possible future successor to Cameron, said after Warsi's announcement that events in Gaza were "utterly horrifying and unacceptable".
"I cannot for the life of me see why this is a sensible strategy," Johnson said on his show on London radio station LBC.
"It is disproportionate, ugly and tragic and will not do Israel any good in the long run."