In an interview with German newspaper Die Welt published on Friday, the chancellor said he hoped the UK would stay part of the union but questioned whether the British people would put up with the status quo for much longer.
"In order to stay in the European Union, the EU needs to change," he said. "The British people are very disappointed with the EU, and the people have the feeling that too many decisions are taken too far away in Brussels.
He added: "Our citizens wonder whether Europe can really solve their most pressing problems and create jobs and wealth."
The prime minister is reported to be prepared to offer an in/out referendum after the next election once he has re-negotiated the terms of Britain's relationship with Brussels.
However Cameron's desire to fashion a looser relationship with the EU could prove tricky. Yesterday a delegation of German MPs told the prime minister not to "blackmail" the rest of Europe with threats.
The Treasury tried to downplay Osborne's comments, telling PoliticsHome there was "nothing new" in the interview.
"We want to remain the EU but the EU has to change, and indeed it is already changing.”