In his opening address, Better Together leader Alistair Darling has said the independence debate is not about "patriotism" but the future of the country.
He described the vote as the "biggest decision we've ever made" but warned "there is no going back" if the Yes campaign wins.
Mr Darling said Scotland must "use the strength of the UK to make Scotland stronger" and said: "We can have the best of both worlds" by staying in the union.
He vowed to ask Alex Salmond questions that "he hasn't answered yet" in the campaign.
The first debate between Alistair Darling and Alex Salmond had barely finished when their respective teams went into battle.
Campaign rivals Alex Salmond and Alistair Darling both traded blows in a surprisingly feisty televised debate on Scottish independence.
Alistair Darling is getting 'feisty' during the STV Debate.