The only referendum

The only referendum on the EU Lisbon Treaty takes place in Ireland today. Interestingly the Irish constitution are holding a referendum because their constitution stipulates a referendum on any treaty that takes away constitutional powers from Ireland. However Gordon Brown tells us that there are no constitutional implications arising from signing the Lisbon Treaty and so the UK does not need a referendum. Both of these positions cannot be true, so are Ireland holding an unnecessary referendum or is Gordon Brown being somewhat economical with the truth?