Prime Minister David Cameron suffered an embarrassing blow in parliament on Wednesday when more than a third of his Conservative lawmakers voted against him in protest at his stance on Britain's membership of the European Union.
Though the revolt was defeated, it could undermine Cameron's leadership, as scores of his own party's lawmakers took the highly unusual step of voting to criticise his government's legislative plans, a week after they were first put before parliament.
The rebels are angry that the government's policy proposals did not include steps to make Cameron's promise of a referendum on Britain's EU membership legally binding.
The party turmoil has fuelled talk of Britain sliding towards the EU exit and has stirred memories of Conservative infighting that contributed to the downfall of former prime ministers Margaret Thatcher and John Major.
While the vote was non-binding, the scale of the mutiny, less than two years before the next parliamentary election, will embolden eurosceptics pushing him to take a harder line on Europe.
A total of 130 lawmakers supported an amendment expressing regret that the EU referendum was left out of the government's agenda. Of those, 114 of the Conservatives' 305 members of parliament voted against Cameron.
A YouGov poll in April put support for withdrawal at 43 percent, with 35 percent wanting to stay in.