Lib Dems "now one of the big three" NICK Clegg will today tell Liberal Democrat activists that there is no going back to being a party of protest or retreating from austerity cuts. The Deputy Prime Minister will use his keynote conference speech in Brighton to say Lib Dem members need to start thinking of themselves as "one of three parties of government." However, aligning his party's journey with the "tough" one the British public are undergoing through the economic crisis, Mr Clegg will also gamble his political fate on a promise that there will be a return to prosperity. In a week that has seen delegates vote overwhelmingly to endorse the coalition's economic strategy despite serious misgiving among members about cuts, Mr Clegg will tell those unhappy with the policy to find a party of protest. Mr Clegg will say: "I tell you this. The choice between the party we were, and the party we are becoming, is a false one. The past is gone and it isn't coming back. If voters want a party of opposition - a "stop the world, I want to get off" party - they've got plenty of options, but we are not one of them. There's a better, more meaningful future waiting for us. Not as the third party, but as one of three parties of government. And a week after he issued an apology for breaking the pledge on not increasing tuition fees, Mr Clegg will talk of his pride in what the Lib Dems have achieved in government. He will say: "I am proud of the resolve we Liberal Democrats have shown over the last two and a half years. We've had some real disappointments: tough election results; a bruising referendum. But throughout it all, we have remained focused, determined, disciplined. It hasn't always been easy, and, when we've made mistakes, we've put our hands up. But we've stuck to our task - and to the coalition agreement -even as others have wavered. He will insist that his party has put to rest "the received wisdom" that the Lib Dems would not be capable of making the transition from opposition to government. He will say: "The Liberal Democrats, it was said, are a party of protest, not power. Well, two years on, the critics have been confounded. Our mettle has been tested in the toughest of circumstances, and we haven't been found wanting. We have taken the difficult decisions to reduce the deficit by a quarter and have laid the foundations for a stronger, more balanced economy capable of delivering real and lasting growth. But, conference, our task is far from complete, our party's journey far from over. Mr Clegg will also appeal to Lib Dem doubters not to fall for the allure of returning to opposition. He will say: "I know that there are some in the party - some in this hall even - who, faced with several more years of spending restraint, would rather turn back than press on. Break our deal with the Conservatives, give up on the coalition, and present ourselves to the electorate in 2015 as a party unchanged. It's an alluring prospect in some ways. Gone would be the difficult choices, the hard decisions, the necessary compromises. And gone too would be the vitriol and abuse, from Right and Left, as we work every day to keep this government anchored in the centre ground. However, Mr Clegg will tell the delegates that that there is no return to the old days of "perpetual opposition." He will tell them to take inspiration from the journey of the British people "from the sacrifices of austerity to the rewards of prosperity."