Scots should not believe the three main parties' promises of devolved tax powers and should vote for independence unless they want to end up with a "paltry", "watered down" offer like the Welsh, Parliament has heard.
Plaid Cymru's economic spokesman Jonathan Edwards insisted the Scottish should dismiss the three main pro-Union parties' promise of more devolved powers, including over tax-setting, as "jam tomorrow" that will be reneged on if Scotland votes No.
Mr Edwards said that had happened to the Welsh as the recommendations of the cross-party consensual Silk Commission for devolved powers for the province had been "cherry picked" and "watered down" by the coalition Government putting together the Wales Bill.
Putting forward amendments that would give the Welsh government more power over infrastructure spending and borrowing, Mr Edwards said it was clear the UK is moving to "far looser union".
During the Bill's report stage, he said: "Now all the unionist parties are falling over themselves to offer increased devolution in Scotland despite having previously said that increased devolution should not be an option in the referendum.
"How they must be kicking themselves now not to have that third option on the ballot paper.
"Who will believe a word they say when they promise their jam tomorrow?
"I would say, based on past evidence, and we've had an inkling of it today by the Treasury Minister (David Gauke), that the only way for the people of Scotland to guarantee more powers for Scotland is to vote for independence.
"I will draw the people of Scotland's attention to the Wales Bill - here we have a Government that set up a cross-party commission to bring forward a consensus, which carefully put together a fully endorsed package of reforms.
"The Conservatives and the Liberal Democrats then reneged on their word by cherry picking and watering down the recommendations of a cross-party commission.
"They then added restrictions and caveats to further render the powers unusable through mechanisms such as the lock-step.
"The UK Government's attempts to strangle the cross-party Silk Commission's original recommendations by adding caveats, restrictions and lock-steps should be a salutary reminder to the Scottish people of the sincerity of Westminster's promises regarding further devolution.
"If the Wales Bill is anything to go by, essentially what the Government here does is make a big headline-grabbing announcement of promising more devolution, only to reveal a paltry offer when the surface is scratched away."
Shadow Welsh Secretary Owen Smith said Labour would support the Bill, but questioned the Government's "seriousness" in analysing the issues surrounding devolving tax-setting powers to Wales.
Mr Smith said: "We see value both in a greater accountability and we see value in the borrowing powers in particular that are associated with income tax and the minor taxes. But we think there are all sorts of reasonable questions to be asked about the impact on his constituents and mine and we feel that the Government is being remiss if not incompetent in failing to deal with these questions and in failing to come to this House with a proper explanation of what they think the impact will be as opposed to using it as a mere stick with which to try and beat Labour."
Mr Smith said Labour had three priorities within the context of the Bill, including to ensure Wales had access to borrowing powers "to offset the £1.6 billion in revenues that have been cut by the Conservatives from the budget for Wales".
Secondly, he said, the Opposition wanted to ensure that "Wales is not further disadvantaged by potential additional cuts to the block grant that are also potentially associated with the transfer of tax powers to Wales".
Thirdly, Labour wanted to "properly test" the costs and benefits to Wales of the transfer of additional tax powers.
He said: "One of the truths thus far of the Bill is that the Government can't really I think be seen to be taking this seriously. Because if they were taking it seriously if this was something they really wanted to do for Wales because they thought it would benefit Wales then they might have done a bit of the work to determine what the net cost would be for Wales and what indeed the benefits will be, but they have undertaken no such analysis. No such work has been done calling into question I think the seriousness with which they address this."
He added: "There are very real concerns, these are not frivolous concerns, concerns about the constituents we represent and the benefit that will be afforded to them by Wales having powers which could be misused in our view in particular by a Conservative Party to cut taxes in Wales in order to engender tax competition across the UK which we see bringing very little benefit but many risks."
Exchequer Secretary David Gauke outlined technical changes to the Bill relating to the tax status of an individual relevant to the calculation of social security benefits.
He said: "The potential hardship that a delay in the calculation of entitlements would cause to individuals makes it essential that we make these amendments to cater for such circumstances."
Welsh Office minister Stephen Crabb said: "The Labour Party seems once again to be mired in confusion over its position in relation to the Silk Commission's recommendations. Those in both part one and part two reports. As is typical now of the party opposite they want borrowing powers but they don't want the means to pay it back.
"They do not want true accountability for devolved government in Wales they just want public spending on the never never. It's just such recklessness, this reckless attitude on behalf of the party opposite that got this country's finances into such a mess in the last parliament.
"This Government, this present coalition Government has no intention of returning to that sorry state of affairs. We are committed to devolving the tax and borrowing powers in this Bill as soon as possible so that the Welsh Government can become accountable for raising the money it spends and accountable for repaying the money it borrows."