Peer urges delay on scrutiny of key parts of Scotland Bill

But the "fiscal framework" governing the funding of these new powers is still under negotiation between the two governments.

Labour's Lord Hollick warned in the Lords that the terms of the framework remained "shrouded in mystery".

He called for the detailed committee stage debate on key parts of the Bill covering tax and welfare to be delayed until the updated fiscal framework has been published.

Lord Hollick chairs the Economic Affairs Committee, which called last week for a halt to the Bill warning that problems with it could put the future of the UK "at risk".

In second reading debate on the Bill, which has already cleared the Commons, Lord Hollick said that without the fiscal framework it was not known how much the Scottish Government could borrow and what would happen if the borrowings could not be paid.

Lord Hollick warned about the framework becoming a recipe for disharmony between the two governments, adding: "Much hangs on the terms and principles of the fiscal framework. It is deserving of very close scrutiny.

"The Government's haste to legislate risks adding insult to injury. Not only is this major constitutional change being made on the hoof, it's also being made in the dark."

Scottish minister Lord Dunlop insisted that the Bill provided the basis of a "stable devolution settlement", making the Scottish Parliament one of the most powerful devolved parliaments in the world.

He said the Bill would ensure that the Scottish Parliament was responsible for raising more than 50% of what it spends - transforming Holyrood from a "pocket money parliament reliant on an annual cheque from the Treasury to a powerhouse parliament the people of Scotland want it to be".

Lord Dunlop acknowledged the critical importance of the fiscal framework but said both governments had agreed not to provide a "running commentary" on the negotiations.

"We are committed to reaching an agreement as soon as we can," he said. "We cannot guarantee when the negotiations will end.

"Both governments need time and space to reach an agreement that is right for Scotland, right for the UK as a whole, and built to last."

The Bill came about as a result of ''The Vow'' made by David Cameron, Ed Miliband and Nick Clegg shortly before the end of the Scottish independence campaign.

It delivers on the recommendations of the cross-party Smith Commission, which examined the additional powers promised by the three then party leaders.

The fiscal framework would govern the funding of the Scottish budget and how it is adjusted once powers are devolved.

A deal is still being thrashed out between the UK and Scottish governments, with the latter threatening to block the Bill's legislative consent at Holyrood unless a satisfactory agreement is reached.

For Labour, Lord McAvoy said that following crucial Government concessions the Bill did deliver on the "vow" and the Smith Commission proposals "in spirit and substance".

Backing the Bill, Lord McAvoy said he was disappointed that the fiscal framework was not available but said both governments had to be trusted to act in "good faith" and deliver for the Scottish people.

For the Liberal Democrats, Lord Wallace of Tankerness also welcomed the legislation but voiced frustration that the framework agreement was not available for scrutiny.

"We can't do this in a political vacuum," he said. "Delaying the Bill at this stage would give the SNP Government effectively a veto on its progressing and I don't believe that is desirable."

He warned that if something went wrong the "finger of blame" would be pointed at the Lords by the SNP.

Former Lib Dem leader Lord Campbell used his maiden speech in the Upper House to warn that an independent Scotland would be less safe in the wake of the Paris terrorist attacks.

"I simply do not believe that an independent Scotland would be capable of providing the level of security which is required if we are to live in safety. And a failure to do so would have dangerous implications, not only for Scotland but for the rest of these islands," Lord Campbell said.

The Lib Dem peer said the case for federalism had never been stronger as a way to reinvigorate the Union.

"If we are to preserve our Union, I believe we need to legislate for a new Act of Union, legislating for England, Wales, Northern Ireland and Scotland, setting out clearly the responsibilities and rights of all four nations," Lord Campbell said.

Conservative former Scottish secretary Lord Lang expressed concern that elements of the Bill could have "dangerous" consequences unless details on how some of its powers would operate were explained properly now.

"No serious consideration seems to have been given to the implications of the Bill's proposals for the Union as a whole. We need to articulate the coherent vision for the future shape and structure of the Union if the ongoing process, reactive, ad-hoc devolution, demand-led and indiscriminately granted, is to be stabilised.

"No major constitutional measure that does not take into account the implications for the United Kingdom as a whole can possibly claim the right to provide for an enduring settlement," Lord Lang said.