The package of new powers promised to Scotland contains "enormous potential" to create grievance between London and Edinburgh, an influential UK parliamentary committee has warned.
The cross-party Scottish Affairs Committee hailed the devolution plans brokered by Lord Smith of Kelvin as offering Scotland the "best of both worlds", combining greater powers and fiscal security.
In a report on implementation of the Smith package, the committee contrasted the proposals with the full fiscal autonomy proposed by the Scottish National party. It argued that the dramatic fall in oil prices meant the SNP plan would have blown an immediate £6.5bn hole in Scotland's budget.
However, the committee's stark warning about the potential for dispute highlights concerns about the Smith package of powers, which includes control over income tax rates and bands and the ability to create new welfare benefits.
Future disputes between the UK and Scottish government over the division of powers could undermine already qualified support for the 308-year-old union between Scotland and England.
The committee, which is dominated by the pro-union Labour, Conservative and Liberal Democrat parties, noted the complexity of establishing a framework for Scottish spending and borrowing.
The Smith package had the potential to become the "enduring settlement" claimed by the government if fiscal rules were "fair, robust and transparent", the committee said. "Get them wrong and the potential for grievance, from either side, will be huge," it added.
The committee noted in particular the Smith agreement on a principle of "no detriment", which means the UK or Scottish government would be required to compensate the other for any financial losses that stem from operation of the new settlement.
Experts have warned that interpreting this principle could be a political minefield, citing such examples as the potential for the UK government to demand compensation if Scottish cuts in air passenger duty reduced the number of people flying from airports in north England.
The Scottish Affairs Committee cited another example of the complex interaction involved in tax policy, saying a Scottish increase in income tax could potentially lead to reimbursement claims from both sides.
The SNP signed the Smith devolution agreement but has complained that the powers it promises do not go far enough and that government draft legislation fails to deliver them fully.
The committee took aim at the SNP's call for full fiscal autonomy, under which Scotland would take over revenues from its geographic share of North Sea oil revenues but would no longer receive a block grant from the UK government.
The committee said that with oil at $60 a barrel, Scotland would receive only about £1.5bn in oil revenues compared with the £8bn in higher per capita public spending it received under the block grant.
The SNP accused the committee of being out of touch.
"The debate in Scotland is about how to get the maximum power for Scotland as soon as possible to counter Westminster's continued austerity and cuts programme - which both Labour and Tories have signed up to for the next parliament," said Angus Robertson, the SNP's leader in Westminster.
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