A couple of tactics by larger banks to unsettle the debate over the liability levy unveiled in this month's federal budget may be working, some key voices in Canberra echoing the industry arguments.Senator Nick Xenophon, one of three Nick Xenophon Team members in the upper house, told the ABC's Insiders program yesterday he supported the levy.On the other hand the Greens are now voicing doubts on this notion, questioning the policy rationale to widen the scope.Xenophon, a deal maker in Senate manoeuvres and proponent of a banking Royal Commission, made clear he wanted to widen the scope of the tax to more banks and also divert some of the revenue to pet priorities with a banking theme."I do support the broad principles and one of the main reasons is that this will give a chance for those regional banks, those community banks, to get a leg up to be able to compete more fairly," he said."I also think it's important that the foreign-owned banks that have a big presence here in this country also be hit with this levy, because that could raise about A$750 to $800 million over the forward estimates and that itself could fund a last resort compensation scheme for the many tens of thousands of victims of financial mismanagement and fraud in this country."Among ministers, assistant treasurer Michael Sukkar has said broadening the scope of the tax to foreign banks remained a possibility, though the prime minister, Malcolm Turnbull, has ruled it out. Lobbying against this option will no doubt ramp up if taken up by government.David Lynch, chief executive of the Australian Financial Markets Association, said recently that the "financial system needs tax arrangements that are internationally competitive and non-distortionary between different types of institution and between different financial products.  "The announced levy on major banks is inconsistent with this approach and sets a poor policy precedent."Chris Bowen, shadow treasurer, made clear early on that the Labor opposition would support the levy, but Bowen has left the party's position open on widening the net to apply to foreign banks. Nor has Labor committed to supporting a quick Senate inquiry on the tax.Bowen and the ALP are at least in line with industry rhetoric damning the government's now six day old insistence on keeping the draft bill a secret, with banking insiders in the know subject to non-disclosure agreements.The Australian Bankers Association on Friday appealed for the federal government to "open up the major bank levy for public scrutiny."In a media release, ABA chief executive Anna Bligh said the four major banks "met Treasury's extraordinarily tight timeframe to lodge their submissions this morning under strict confidentiality."The association and each bank, for now, "cannot quantify the impact of this tax on banks, and the flow on effects to customers, because the legislation has not been in the public domain," Bligh said.A query on the scope of the "impact" of the tax is about the only crumb to have leaked from industry executives to the media."The revenue projections would fall