Unionist peers have rounded on the Scottish Secretary for refusing to approach the European Union's governing body for advice on Scotland's future.
Michael Moore has been accused of adopting a "puzzling, unsustainable and totally irresponsible position" by refusing to approach the European Commission (EC) for confirmation of what would happen if Scotland became independent.
Former Tory Scottish Secretary Lord Forsyth, an arch-critic of devolution and independence, suggested Scottish Finance Secretary John Swinney had a point when he criticised the UK Government for not exercising its exclusive power as the EU member state to talk to the EC.
Fellow Tory peer Lord Lawson said Scotland is "perfectly capable of being independent" and accused Mr Moore of letting the nation down badly by refusing to explore the full consequences of a yes vote.
Labour peer Baroness Kingsmill described Mr Moore's position as "quite astonishing".
But Mr Moore argued that there was no need to speak to the EC given the amount of information in the public domain already, including a letter to the committee by EC president Jose Manuel Barroso which suggested Scotland would have to reapply to the EU as a new member state.
Mr Swinney told the committee last week that there was no provision in EU treaties to support Mr Barroso's view, a position echoed by former European Court judge Sir David Edward yesterday.
Mr Moore said: "We have not directly gone to the Commission. We have not seen the need to do that.
"We have looked at the broad range of evidence that is in the public domain already, but it was helpful that in response to your inquiries as a committee that we have got that further confirmation (from Mr Barroso).
"I think John Swinney is fundamentally wrong."
Committee chairman Lord MacGregor said: "That actually means that if there is a yes vote and some of the terms of the negotiation into the EU are very onerous for the people and economy of Scotland, and some of the other issues related to the Bank of England and so on, there is a sort of blind vote in the referendum and then people will have to wake up to some of the consequences once it is negotiated."
Mr Moore added: "I'm not going to play down the uncertainties, and indeed it is the Scottish government's unwillingness to acknowledge uncertainty that has hampered the debate."
He added that "shadow negotiations" on the EU would be inappropriate amid all of the other uncertainties surrounding independence.
Mr Moore said he believed Scotland could be independent, but argued: "The question for me, and I think this is true of people across Scotland, is: would that be better for us? Would we be more secure? Would we have greater economic opportunities?
"It is my view, and the view of the government, that the answer is no - we would be much better within the UK government.
"We don't want to assert that, however."
He said he will work to iron out as many of the uncertainties surrounding independence as possible in the UK government's under-construction Scotland Analysis Programme, but advised that the UK Government "will not pre-negotiate" the terms of independence.
Baroness Kingsmill said: "It is slightly irresponsible for the government not to focus on what the economic consequences might be in advance of a referendum.
"I'm astonished by your remarks that there will be no negotiations, there will be no discussion, there will be no exploration of these economic consequences for the UK."
Mr Moore said: "I regret the uncertainty, but the reality is that we are not in a position where we can create the hypothetical circumstances to understand what the negotiations would be.
"We don't have a position in government that separates Scottish interests out from UK interests."
Former UK Chancellor of the Exchequer Lord Lawson suggested Mr Moore's position is "totally unsustainable".
"Leaving aside, for the sake of simplicity, the rest of the UK, I think you are letting down very badly the people of Scotland," he said.
"How are the people of Scotland to judge this if you are not prepared to say in your judgment what the consequences would be?
"That seems to me a totally unsustainable position."