THE timing of last Thursday's Fraser of Allander/Herald Group seminar on the country's fiscal future could have been better for Michael Moore MP, the Liberal Democrat Secretary of State for Scotland.

The fact that the Scottish Parliament had voted to pass the Scotland Bill only a day earlier, clearing the way for it to complete its passage through Westminster, would ensure that the legislation was at the top of the evening's agenda.

With former Scottish Lib Dem leader and finance spokesman Tavish Scott and Jeremy Purvis already leading a cross-party push for more devolution than is contained in the bill, and even the prime minister dangling new deals should Scotland stay in the union, Moore's duty to talk up the legislation as its leading backer was always going to be awkward.

The Sunday Herald's Iain MacWhirter, chairing the seminar, threw the first brickbat during the introductions by asking whether the bill was already an anachronism. We were now in what he called the "bizarre situation" where the SNP had waved through the legislation despite failing to secure any of their six demands for extra powers, while the three main unionist parties had "disowned it or at any rate are looking at it as a stepping stone to something else."

When Moore reached the podium in his usual urbane manner, despite having been late from a delayed flight from London, he joked he was "wound up" by this description.

"That's not quite how I see it," he said. "If as Secretary of State you can't be in favour [of your own legislation], who else can I expect to be?"

He added: "The thinking will move on, but that's not to disregard what's in the Bill. What matters is that we have now established financial accountability for the parliament and we can begin to look at how it can be developed further. That debate has barely started."

Moore described the Bill – not for the first time – as the "biggest transfer of financial powers since 1707".

However Jim McColl, head of Clyde Blowers and one of Scotland's top businessmen, drew few positives from the package. He complained that the Calman Commission, whose proposals form the basis of the new legislation, had been unable to do anything constructive because it was briefed not to recommend anything that would advantage Scotland over the rest of the UK. His hackles were raised, he said, by the Secretary of State's line about it being the biggest transfer of powers in history.

"The Scotland Bill does nothing to address the problem of how to stimulate business," he said. He doubted whether the Scottish parliament would ever use the new power to set the income tax rate 10p lower or 10p higher than the rest of the UK. "I don't think there's any stimulus in there to differentiate [Scotland]. I think it's pretty bleak," he said.

MacWhirter suggested to Moore that it was an "open secret" that the 10p power was designed not to be used. When Moore dismissed this as the sort of thing you would expect from "cynical journalists like you", the chairman asked if he would match McColl's bet in the other direction.

"I think it will be [used]," Moore replied. But he added with a smile that it was too early to start talking about wagers.

The evening's other main critic of the Scotland Bill was Professor Andrew Hughes-Hallett of the University of St Andrews and George Mason University in Virginia, who has been one of the leading pro-separation academic voices for some time.

He started his speech by railing against the controversial cover of the Economist magazine from earlier this month that suggested an independent Scotland would be impoverished. It was badly argued, he claimed, since its analysis of Scotland's prospects assumed we would make no changes to the policies that are currently being pursued.

He rehearsed various technical but arguably important points that he and other specialists have made before for why the income tax policies in the new legislation are not going to be very helpful to Scotland. For example one is about the fact that the part of the income tax revenues that will still be paid by block grant from Westminster will continue to be affected by forecasts that have consistently over-estimated what Scots will earn and pay.

This has meant that the grant has later had to be reduced to balance the UK's budget. With the Office of Budget Responsibility's forecasts through to 2016 predicting 1% faster income tax growth in Scotland than elsewhere, in line with past over-estimates, he said there was a problem of "transparency and verifiability" about how these forecasts are calculated. More generally, he complained, the Scotland Bill only gives Holyrood control over 9% of the revenues from taxes raised in Scotland. The Bill might create some accountability, but the more important need for responsibility is not being served.

While making the case for devo max, meaning transferring all tax-raising powers to Scotland except VAT, Professor Hughes-Hallett showed two tables that sparked some of the most heated debate of the evening.

One, which was about fiscal surpluses, showed that if Scotland chose independence the UK would have to borrow proportionally more per head of the population than at present.

The second was about the predictability of different revenue streams. It indicated that some tax-raising powers such as corporation tax were much less subject to variation than the block grant. His point was that if corporation tax powers were transferred to Scotland, the Scottish Government would have a more stable budget than at present.

Professor Gavin McCrone, one of the country's top economists, attacked his fellow academic from the audience once the floor was opened to questions. "When Andrew Hughes-Hallett showed Scotland was in surplus next to the UK, it's important to clarify it's because of oil revenues," he said. "We don't know how oil will be split [if Scotland opts for independence]."

He said it was "still to play for" and that it would be heading down in future in any case. In relation to Hughes-Hallett's other chart, he added that oil tax revenues "fluctuated enormously".

Hughes-Hallett said this latter point was "nonsense", since all sources of tax revenue were variable. His chart was merely about showing the order of variability and hence which ones it was in Scotland's best interests to control. On the future of oil revenues, he snarled: "The Economist argued that the quantity of [North Sea] oil is going down by 6% a year, but revenues on average are up 11% so prices are rising by 17%. Are you expecting prices to go down?"

After McCrone made some remarks about unpredictability through the likes of shale gas potentially dragging prices down, Hughes-Hallett continued: "The real point you should have made is that we should be diversifying away from oil..."

Professor Andrew Goudie, until recently the chief economic adviser to the Scottish Government, who was also on the panel, drew on this oil debate to underline his theme about the need to spend more time focusing on the risks around devolution and independence and less time talking about the broad options.

"The real question that needs to be thrown at people ... is what do they see as the shock absorbers in the system when oil prices vary? ... We have been attempting to diversify since devolution ... What are these shock absorbers that will allow the economy to be smoothed over time?"

More broadly on corporation tax, Goudie believed that focusing on devolving it meant being "naive" about the ability of corporations like Barclays and Amazon to avoid paying it, and the fact that the EU would not allow any other member to "do an Ireland" and make cuts big enough to have the necessary impact on inward investment.

Neither McCrone nor Hughes-Hallett carried on the corporation tax debate regardless. McCrone argued that allowing Scotland to set rates would upset other needy regions and create a "political problem that's very difficult to resolve".

Hughes-Hallett shot back that other jurisdictions such as Canada, the US and Switzerland all managed to devolve the tax without any drama or any race to the bottom. "They stabilise," he concluded. "I don't see why we can't do it. We are not sub-human."