LONDON, Dhu-AlHijjah 19, 1436, Oct 3, 2015, SPA -- Britain will vote to leave the European Union in a planned referendum if it does not secure "robust, substantial and irreversible" reforms, the foreign secretary has warned, in a marked hardening of language on the issue, Reuters reported. Prime Minister David Cameron has promised to renegotiate Britain's EU ties ahead of a vote on membership by the end of 2017. He favours staying in a reformed EU but has said he will rule nothing out if he cannot secure reforms, which include curbs on welfare payments to EU migrants. Most opinion polls show a majority of Britons back staying in the EU, but the gap with those wanting to leave has narrowed in recent months. The migrant crisis has boosted calls for Britain to regain greater control of its own borders. British Foreign Secretary Philip Hammond said European leaders needed to know that Britain was not bluffing over the issue, and said Cameron's ministers would decide how to vote only once they had seen the changes proposed by Brussels. --SPA 14:57 LOCAL TIME 11:57 GMT www.spa.gov.sa/w