Today's report on the economic consequences for Scotland and the rest of the UK of a Yes vote in the 2014 independence referendum promises "an objective account".

It claims not to make the case for or against independence. That is somewhat disingenuous from the House of Lords Economic Affairs Committee, given that the instincts and politics of its membership are entirely on the pro-UK side. In fairness, that was inevitable since the SNP has no peers as a matter of policy.

Nevertheless, anyone looking for danger signs would notice the report cannot resist bringing up Scotland's disastrous Darien Scheme in its second chapter. The report rightly raises many of the issues the Yes campaign must address if it is to have any hope of victory. In particular it homes in on the SNP's wildly optimistic timetable for independence and the whole issue of economic stability. Yet it is too easy to dismiss the entire exercise as a publicly funded contribution to the Better Together campaign on account of its authorship.

Though John Swinney, Scottish Finance Secretary, and Patrick Harvie of the Scottish Greens gave evidence to the committee, and though the UK Government is criticised for failing to engage with the independence debate, the most powerful word in this report is "but". For example: "An independent Scotland would benefit substantially from tax revenues from a geographical share of North Sea oil and gas reserves. But, as the revenue from North Sea oil and gas would be a much larger proportion of total tax revenue in an independent Scotland than in the UK, its volatility would make it more difficult to conduct economic policy."

Even when it gets around to listing what could be the real benefits to Scotland of independence – making its own choices on tax and tailoring economic policy to play to Scotland's strengths, for instance – it manages to hedge the argument with so many caveats as to cancel out any impression of objectivity. The bottom line is that there are "clear threats to Scotland's prosperity under independence, while the upside is uncertain", according to Lord MacGregor and his committee. Though they pose valid questions about currency, the division of assets and debts, EU membership, bank regulation, defence and the rest, it is hard to find much that has not been asked already.

The SNP is happy to seize on criticism of the Coalition for failing to take Scottish independence seriously. This will change nothing as ministers at Westminster know pre-negotiating issues such as the relocation of Trident and the division of assets could give the Yes campaign real momentum. The Yes campaign may be refusing to admit to any downside to independence. By the same token, a report that seems blind to the upside falls into the same trap.