How national insurance distorts the picture of tax rates for richer and poorer

I agree with Patrick Collinson that politicians massage the headline rates of income tax, and changes in employee national insurance attract much less attention (Money talks, 22 February). However, employer NI contributions are also a form of taxation on employment but are even more cunningly concealed.

For someone on the minimum wage of £8.21, the effective marginal rate of tax is 45.8%, made up of 20% income tax, 12% employee NI and 13.8% employer NI. The marginal tax rate for someone on £26 an hour is 55.8%, made up of income tax at the higher rate of 40%, employee NI of 2% and employer NI of 13.8%. In this case the increased income tax rate exaggerates the liability of higher earners when in fact the 10% difference in effective tax rates is half the headline difference in income tax.
John Oliver
London