The Unionist parties behave like balls on a pin table – not knowing which direction to face on the constitutional debate.

Their latest agenda appears to be the imminent Institute for Public Policy Research report by academic Alan Trench "a constitutional expert" ("SNP snub for more tax powers", The Herald, January 21). Incidentally, they are really snubbing devolution.

From pouring money into Scotland in the post-war years to thwart the SNP to promoting devolution to kill nationalism stone dead and, following the SNP's historic election victory in 2010, the discredited Calman proposals that would make Holyrood "more" accountable, they now declare that Scotland could not survive on projected oil proceeds. Neither could Westminster. The devolution settlement is a failure and Calman, upon which they stood shoulder to shoulder, is to be replaced by one or other of the plans currently under consideration by Labour, the Conservatives and the Liberal Democrats separately.

The LibDems recycle their federal mantra, which should find favour with Mr Trench who has simply reworked the figures in GERS. Indeed, the only named political representative at his launch at the Royal Society Edinburgh on Friday is their Scottish leader Willie Rennie. Better Together leader Alistair Darling might feed some of the ideas into the Labour review, while the Conservatives will be targeting SNP voters who do not favour independence – that should be fertile hunting ground.

Given Mr Darling's party's role in getting the Union into such a financial mess, his advice on preventing a repetition will also be of value to the SNP.

The Unionists don't seem to get the big picture. They never stop linking independence with personal invective against SNP leader Alex Salmond. They even challenged him about which of the Calman proposals he would adopt when he won in 2016. But the independence referendum is in 2014, and the next Holyrood election is in 2016. A Yes vote could be followed by a Unionist party victory in 2016. Even more bizarre, a No vote in 2014 could be followed by an SNP victory in 2016. And so the speculation goes on.

Douglas R Mayer,

76 Thomson Crescent, Currie, Midlothian.