Britain is prepared to take its sanctions against Russia to a ‘ whole different level ’ if Vladimir Putin ramps up his aggression , David Cameron has said . The Prime Minister said the Russian president has ‘ ripped up ’ the rule book and could not expect still to have access to international markets and finance . He said the West must be prepared to ‘ settle in for a long and determined position ’ against the Moscow government and that further incursions into Ukraine should be punished . David Cameron , pictured left , has said Britain is prepared to take its sanctions against Russia to a ‘ whole different level ’ if Vladimir Putin , pictured right , ramps up his aggression . Mr Cameron told the Wall Street Journal : ‘ If Russia is going to rip up the rule book of the 21st century and destabilise a sovereign country , then the rest of the world should be prepared to say to Russia , well you can ’ t rip up one part of the international rule book while still having access to international markets , international finance , international systems. ’ On continuing tensions in Ukraine , Mr Cameron said leaders had agreed to implement tougher sanctions against Russia if the ceasefire fails . Despite last month ’ s ceasefire , violence has continued to flare up across the region . Mr Cameron also reiterated his commitment to hold an in-out referendum on Britain ’ s membership of the European Union in 2017 . While he believes the ‘ right answer ’ is for Britain to remain in the EU , Mr Cameron said he accepted that the country might vote to leave . He added : ‘ You can ’ t stay in an organisation if your employer , the British public , doesn ’ t consent to it. ’ Cameron , pictured left , said Putin , pictured right , had 'ripped up ' the rule book and could not expect access to international markets and finance . The conflict in the east of Ukraine has plunged ties between Russia and the West to Cold War-era lows as Kiev , along with the US and the EU , say they have evidence that Moscow is arming the rebels and boosting their ranks with regular army soldiers . Russia has denied the accusations . The threat of an immediate cut to the gas supply from Russia to Ukraine was averted yesterday . Russian gas exporter Gazprom said it had received a prepayment that was enough to cover about five days of supply .
David Cameron says Russian president has 'ripped up ' the rule book . Says PM could not expect access to international markets and finance . Putin says further incursions into Ukraine by Russia should be punished .