John Whitehead, secretary of New Zealand's Treasury, yesterday called for debate over the introduction of capital gains on investment property.Whitehead made the comments in a speech to the New Zealand Institute of Company Directors in Wellington. In a speech framed in the context of New Zealand's low productivity, ageing population, dependency on foreign-born labour and comparatively high levels of company tax Whitehead asserted that "the government's revenue base will be unsustainable in the medium term .... More broadly, the tax system as it is currently structured does not seem fit for growth." Noting that the tax system tended not to encourage either investment or immigration, Whitehead called for lower effective marginal tax rates and also a tax policy that shifts investment incentives.He advocated "moving the boundaries to tax more capital gains - for example on investment property - and shifting more of the tax base towards consumption."