Tax on earned v unearned income

As the recently published tax returns for our PM show, he saved £300k in tax on capital gains. Is it fair for people holding investments to pay about half the tax of people getting income through their salaries (Dan Neidle of Tax Associates quote).? It is the Tories who have significantly dropped these rates, claiming it would encourage business investment. Yet to see that!! Personally I'm with giving better tax breaks to the working person and at least balancing out the unearned income tax rate!