UK governments 'failing on devolution'
Successive UK governments have failed to adapt to devolution - with a new mindset required in order to save the Union, according to a House of Lords committee.
The Constitution Committee said devolution across the UK had largely been "demand-led and piecemeal".
And they said there had been a lack of strategic thinking about the wider impact of devolution on the Union.
Peers also called for the Barnett Formula to be scrapped.
The formula, which is used to distribute funds across the different parts of the UK, should be replaced by a new needs-based system, their report said.
It said power had been transferred to Scotland, Wales and Northern Ireland in "an ad hoc, piecemeal fashion", without "proper consideration of the cumulative impact of devolution on the integrity of the Union".
It warned that this "inattentive approach to the integrity of the Union cannot continue", with the Lords calling for any further plans to transfer power out of Westminster to be "considered within an appropriate framework of constitutional principles that safeguard the integrity of the Union".
In future, a "Devolution Impact Assessment" could be published, examining the potential impact of proposals on the "cohesiveness and stability of the Union as a whole, and on each of its constituent nations".
Ministers have also been urged to adopt a new approach to devolution, with the report saying: "A new mindset is required at all levels of government - one that recognises the devolved institutions as now being established components of the UK's constitution.
"This new mindset will require abandoning a 'devolve and forget' attitude.
"Instead, the UK government should engage with the devolved institutions across the whole breadth of government policy, co-operating and collaborating where possible.
"In particular, the Joint Ministerial Committee should be reformed to promote co-operation and collaboration, rather than grandstanding and gesture politics."
'Group of cronies'
The report also said it was "too soon to know" whether English Votes for English Laws (Evel) and "devolution deals" - where local authorities are given greater power - would provide an answer to the "English question", which has left the largest part of the UK as the only part without its own assembly.
Responding to the report, SNP MP Pete Wishart claimed the committee had shown a "spectacular failure to grasp devolution".
He added: "This House of Lords report is irrelevant and adds nothing to the debate. The decisions about the future of the government of Scotland should rightly be made by the people who live and work here.
"Decisions about Scotland's future should not be left to a group of cronies and politicians who have been rejected by the electorate and have no democratic accountability whatsoever."