High earners considering getting round next year's 50p tax rate by converting income into more lightly taxed capital gains are being lured by the 'glister of fool's gold', according to a top HM Revenue & Customs official. Dave Hartnett, HMRC permanent secretary for tax, pledged action against avoidance schemes, which is one reason the Treasury expects to collect only 30% of the potential yield from the 50p rates, reports the Financial Times. 'For HMRC, a 70% attrition rate or tax gap in respect of the 50% rate would not be acceptable. We are keeping such schemes under very close scrutiny and where such schemes are seen to work technically, we will not hesitate to go to our ministers to ask for a change to the legislation,' he told a meeting in Madrid. Jon Terry, a partner at PricewaterhouseCoopers, told the FT that some planning approaches were likely to be acceptable, as long as they were genuinely commercial arrangements that involved a transfer of risk to the employee. Experts said one acceptable approach might be to issue nil-cost share options. An employee could choose when to exercise the option and trigger the income tax bill over a period of between three and 10 years, which might coincide with a reduction in the tax rate. Shadow chancellor George Osborne has said the 50% rate should not be 'a permanent feature' of the tax system.