The former prime minister Gordon Brown has said there is "a clear common sense" argument for Scotland to remain part of the United Kingdom, after launching Labour's pro-union campaign.
Scottish First Minister Alex Salmond revealed in March that a referendum on independence would take place in September 2014.
Addressing a rally in Glasgow, Mr Brown said that Scottish values can best be realised as part of the UK and that Britain is strongest when pooling its resources together, citing the examples of the NHS, mining, shipbuilding and other core industries.
But Scottish nationalists have dismissed his claim that taxes would have to rise to fund its welfare plans if the country was granted independence.
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