The Trainspotting writer, who has spoken out in support of independence on several occasions, said he believes the September vote will be close run.
Welsh told online magazine Curious Animal: “It’s part of the secular decline after the two world wars and the building of the welfare state and all the things that held Britain together that don’t really exist any more.
“I think it’s inevitable it will happen. Whether it’ll happen this year or not, I don’t know. It’ll be a close run thing.
“The British economy is in a mess and it’s going to be a mess for the next few years. People might just think they’ve been paying through the nose and it’s time to go.”
He added: “I would love to see it happen but, more than Scottish independence, I’d love to see English independence; England could be the multi-cultural, post-imperial democracy it was meant to be. I can vote because I’ve got part-residency in the UK but I won’t vote. It’s up to people in Scotland to decide what they want to do.”
Meanwhile, First Minister Alex Salmond yesterday said David Cameron is “everything wrong” with British politics.
He added: “The problem for the No campaign is they keep saying that we are going to hear a positive case for the Union but when they come to deliver their message it’s the same old negative whining and running down of Scotland. Scotland has moved beyond the fearmongering of David Cameron.
“And he personifies everything that is wrong with the politics in this country at the present moment.”