The report claims that tax thresholds are not being raised in line with wages meaning that, while 3.7m taxpayers paid the 40p rate last year, this figure will rise to five million by 2014, reported the Daily Mail.
Motivating The Middle has been published by Conservative MPs Kwasi Kwarteng and Priti Patel.
It argues the problem has been caused by the threshold rising slower than earnings under New Labour, and the level at which 40p tax falls has then been lowered by Chancellor George Osborne as he raises the tax-free personal allowance.
The 40p tax threshold is due to fall again to £41,450 next year, for most earners, from its current £42,475 level.
Kwarteng said: ‘When Lloyd George brought in his ‘supertax’ in 1909, it was only paid by those on around the equivalent of £500,000 a year. Now the higher rate of 40% income tax is increasingly paid by those in the middle class.”
