The architect of the 40p tax rate, Lord Nigel Lawson, has called for Prime Minister David Cameron and Chancellor George Osborne to scrap the tax bracket as too many middle-income professionals have fallen into the higher band.

Lord Lawson, who introduced the 40% tax rate 25 years ago, said pushing more "middling professionals" into the tax band would be a "mistake."

"Far too many people are paying the 40% rate. The total should be much closer to the number when I was chancellor," Lord Lawson told the Telegraph.

"It was intended for the rich, the well-off. The people who are paying it today are middling professionals who should not be in the higher rate.

"If you earn £45,000, you are neither rich nor poor – you are in the middle. You are certainly not rich. No one on £45,000 should be paying a marginal rate of 40% tax."

While the Tories have pledged to help the poorest Britons by raising the tax-free personal allowance, which has dragged more than two million people out of the tax system, middle class pockets have become increasingly tight as wage rises drag more people into the higher tax band.

The 40% tax band was introduced a quarter of a century ago by the former Conservative Chancellor Lawson.

At the time, only one in 20 people paid the higher rate, compared to one in six people today.

This equates to about 1.35  million in 1988, compared to 4.4 million people in 2013.

Over the next year, this number is set to rise to five million.