The Conservatives do not have a majority in parliament which is why they are in a coalition with the LibDems. They do not have a majority because not enough people voted for their policies. The LibDems are a pro European party and are not ashemed to say so. Which is why the EU referendum bill is a private members bill from a backbench Conservative MP and not a Government bill. If it were a Government Bill its passage into law would be speedy and straight forward.
Whenever the Conservatives have had a majority, they have never given the people a vote on Europe. They took us into the EEC without a vote. It took a Labour Government to let the people to finally have a vote. Before the last election Cameron promised a referendum on the signing of the Lisbon Treaty. But the small print on that promise was "if it hasn't already been ratified" , knowing full well that it would be.
This Private members Bill is again a con. If the Conservatives really wanted you to have a vote they would have set the wheel in motion shortly after they formed a Government. Instead, they introduce a Bill with the clock ticking down to the next election. Because of the short deadline, Labour can delay the Bill in the Lords meaning it is u likely to make it into law in time.
Cynics like me believe the Conservatives were well aware of that possibility and never intended delivering a referendum. The sole purpose of the bill was to play the blame game, that the OP unfortunately falls for easily.
Labour and the LibDems believe the country is better off in Europe so they don't want us out. They do not trust the electorate to make the right decission in a referendum, so they won't give them an opportunity.
The Conservatives are tied in knots by Europe and have been for 40 years. The Conservative leaders think the same as Labour and the LibDems, and want to stay in Europe, but they are afraid to say so. Grassroots Tories are anti EU. Which is why this whole charade is taking place. Cameron promises something he can't deliver. Labour kill it. Cameron says I tried but the nasty lefties stopped you having a vote.
If the Conservatives were genuine, they would abandon the vote tomorrow and they would guarantee the a Referendum on Europe withina year, if the Conservatives win the election with a majority. Let the people decide.
But they won't.