The choice we face is clear - believe Alex Salmond or believe the experts and the facts. As part of the UK, we are better placed to tackle the long term challenge of sustainable public finances. Things are difficult just now, but the IFS report makes clear that they would get much worse if we separated from the UK. That is a risk that we really don't need to take. Coming little more than a week before the publication of the SNP's crucial White Paper, the IFS report poses a significant challenge for Alex Salmond. The White Paper must face up to the consequences of independence, including the need for big spending cuts and tax rises. If it doesn't, then it won't be worth the paper it is written on.