The debate has moved on to the second topic, Scotland at Home, with several questions from the audience focussing on the NHS.
Mr Darling says that the NHS in Scotland receives higher public expenditure per head of population that in the rest of the UK, drawing attention to Scotland's "ageing population".
First Minister Salmond argues that there is growing privatisation in the NHS under the current British government.
With just a few weeks to go until the Scottish independence referendum takes place, here are some key facts about the vote.
An investigation has been launched after listings appeared on eBay offering to sell votes in the upcoming Scottish independence referendum.
Bounce for leaving the union following second debate this week, but only 43% expected to vote yes in referendum on September 18