True enough, the 2005 Labour manifesto promised to put any EU constitution to the public - but that promise was dependant on their being a ratified constitution, and there wasn't, because it was rejected by the French and Dutch.

Instead we got the Treaty of Lisbon, which wasn't a constitution. It was this Treaty that got initially narrowly rejected in an Irish referendum, but then accepted when presented again for a second referendum with some slight (but significant) adjustments - thus demonstrating that Ireland is a considerably more democratic country in this respect than the UK. Support for EU membership in recent polls in The Republic runs at around 84%.