In killing the referendum, this government destroyed its legitimacy. Without making a promise to hold a referendum, Labour could well have lost the last election, as the clear choice between Labour and no referendum or Tory and a referendum would have pushed a number of people to vote Tory, quite possibly enough to swing the election. Do not forget Enoch Powell famously voted Labour in 1974 on this same issue.
Things have moved on. The EU has got its treaty ratified and has no intention of letting the people interfere with its plans. Like Ceausescu on the balcony, they will not listen until we force them to listen. Now is the time to make that happen.