* Schemes involving tax-free or low-tax countries to be reported
* Preferential tax regimes in EU states in the spotlight
* Penalties to be decided at national level
BRUSSELS, June 21 (Reuters) - Tax advisers in the European Union risk fines for helping companies to cut their tax bills by shifting profits to low-tax countries, if proposed new EU legislation gets approval.
Under the draft law, proposed by the European Commission on Wednesday, tax advisers including the Big Four accounting firms, banks and lawyers, would be required to inform authorities about "potentially aggressive tax planning arrangements" set up for their clients.
Britain, Ireland and Portugal have already introduced penalties for intermediaries favouring tax avoidance but the new law would apply across the EU, although penalties would be decided by national governments.
In Britain, the measure was recently introduced and is estimated to have reduced tax avoidance by "over 12 billion pounds" ($15.2 billion), EU tax commissioner Pierre Moscovici told a news conference.
Schemes involving transactions to tax-free jurisdictions, such as Jersey, Guernsey or the Cayman Islands, would have to be reported.
The new disclosure obligation would also cover cross-border arrangements whereby companies may shift tax liabilities to EU countries with "preferential tax regimes".
The planned legislation is part of a set of measures adopted by the European Union after last year's Panama Papers and other revelations of widespread tax avoidance by wealthy individuals and big companies through carefully constructed schemes.
EU officials said examples of preferential regimes would include a tax rebate offered by Malta to foreign-owned companies, which can slash the tax rate to as low as 5 percent; patent box regimes in several EU countries that allow firms to pay less tax on intellectual property revenues; or cross-border tax incentives for specific industries.
Tax planning schemes benefiting from these arrangements present "a strong indication of tax avoidance or abuse" and therefore would need to be reported to the tax authorities, the European Commission said. However, EU officials stressed that this does not automatically mean that these arrangements were illegal.
The Association of Chartered Certified Accountants (ACCA), a global body, welcomed the proposal as a way to curb abusive tax planning but warned against the risk of a flood of disclosures.
"The fear of inadvertent non-compliance and the penalties that will result may drive some tax professionals to over-disclose, just to be on the safe side," Chas Roy-Chowdhury, head of taxation at ACCA, said stressing that an excess of information could make the fight against tax avoidance less effective.
But some EU lawmakers saw the proposal as having little relevance in tackling tax avoidance. Markus Ferber, a German lawmaker of the European People's Party, the largest in the legislature, said it "will not be a game-changer".
"The EU is just not credible as long as there are inner-European tax havens and some member states keep systematically undermining their neighbours' tax base," he said, adding that tax advisers were likely to avoid disclosure by citing their professional discretion obligations.
The draft law dictates "effective, proportionate and dissuasive penalties" for non-compliance, but leaves EU states free to decide sanctions or fines at national level.
EU leftist lawmaker Fabio De Masi called for tougher sanctions, including the removal of business licences for advisers promoting aggressive tax planning.
Under the new law, if there is no intermediary, or the tax adviser is located outside the EU, the obligation of disclosure would fall on the taxpayer using the arrangement.
The proposal will need the approval of the European Parliament and all EU states to become law.
Some EU states have shown little appetite to move fast in the fight against tax avoidance, saying it could hamper the competitiveness of European companies. ($1 = 0.7882 pounds) (Reporting by Francesco Guarascio zfraguarascio; Editing by Susan Fenton)