The K2 tax-avoidance scheme Carr is said to have used enabled members to pay income tax rates as low as 1%.

BBC: Tax avoiders should be named and shamed, says watchdog

For decades, the Internal Revenue Service has asked courts to look past the fancy lawyering and examine the substance of a tax-avoidance scheme.

FORBES: Tax Case Asks Whether IRS Flip-Flopped On Key Position

Allow HM Revenue and Customs to declare any scheme designed purely to allow the avoidance of tax "null and void" in law.

BBC: Bill-by-bill: Guide to MPs' private members' bills

Despite all this talk about tax avoidance, the chancellor also gave the green light to a "shares for benefits" scheme which was first suggested earlier in the year.

BBC: Plugging the leaks in the tax system