David Cameron is facing renewed backbench disquiet over the European Union after he tried and failed to satisfy Conservative demands for a referendum.
Conservative MPs warned that the Prime Minister had not gone far enough by declaring that he would consider calling a referendum - but not yet.
Later today, Mr Cameron will make a statement on Europe to MPs in the Commons.
Former defence secretary Liam Fox has said that the UK should leave the European Union unless there is a rebalancing of their relationship.
Foreign Secretary Hague said there would be a "very, very powerful" case for a referendum if Europe moved towards a more federal system.