More than 1.7 million workers are facing being paid below the new national living wage within just four years of it being introduced.

According to research by the Social Market Foundation (SMF) a total of almost 1.9 million people will not receive the wage when it increases from its introductory rate of £7.20 an hour to £9 an hour for over 25's in 2020.

The reason for the expected wage gap is because "the rate does not cover the self-employed", researchers say.

The study, funded by the charity Trust for London, also raised fears that companies might move away from directly employing workers towards contracting out services to the self-employed.