The leaders have continued to clash over the issue of cuts to welfare and the NHS.
Mr Salmond says the British government prefers to spend money on defence - and the Trident nuclear deterrent - than the NHS.
Mr Darling says "on the issues of welfare reform ... I believe we can best do that with the strength of resources that come from being part of the United Kingdom".
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