Attending his final EU summit in Brussels before polling day on 7 May, the Prime Minister brushed off a warning by European Council president Donald Tusk that achieving the treaty changes he needs will be “almost Mission Impossible”.
He said he is confident he will ultimately prevail, like Tom Cruise in the Mission Impossible films.
“If you watch any of his movies, Tom Cruise normally prevails in the end. He is a little bit smaller than me but I hope to be just as effective,” he said.
“The point is that if I come back after the next election I will have a mandate and a mandate to deliver change in Europe. That mandate will be very powerful.
“If you have a mandate for change I think that mandate will be taken seriously, those changes will be achievable and it is very, very important for the country that we do that.”
Mr Cameron made clear Europe would be central to the election campaign, appealing to voters to give their “full-hearted backing” to his plan to re-negotiate the terms of Britain’s membership and then put the outcome to the country in an in/out referendum.
“I am confident that we can get what we need. But it will help – in fact, it is absolutely essential – to have the full-hearted backing of the British people,” he said.
The Prime Minister acknowledged there were some EU leaders who would be glad to see the back of him if he was defeated.
He said the election of Labour leader Ed Miliband would send a message: “You can all relax – no renegotiation, no referendum, no difficult choices, no difficult reforms.”
He added: “I am sure there will be some people in Brussels who will breathe a sigh of relief that I’m not here because they quite like to have the easy life, they don’t want the referendum, they don’t want the re-negotiation, they don’t want the changes.
“But they’re necessary, they’re right for Britain and that’s why this election, when it comes to Europe, is so important.”
He said he would work around the clock to fight for British interests. “If it is four o’clock in the morning and you have to work to get the budget cut, I’m here and I’m doing it.
“If it’s four o’clock in the morning that you need to be here to veto a treaty that is not in Britain’s interest, I’m here and I’ll do it,” he said.
“However long it takes, whatever the working hours are, you will never find me absent from the fight.”
Mr Cameron said he could advance Britain’s interests in Europe, securing an extension of EU sanctions against Russia until the terms of the ceasefire deal in eastern Ukraine are honoured.
He said he has also pressed for a resolution of the dispute between Greece’s left-wing Syriza government and the country’s eurozone creditors.