The chief executive of Aviva Investors has warned that millions of low-income investors “swept into” index-tracking funds thanks to UK pension reforms face a rude awakening in an inevitable market downturn.

Euan Munro, who took over as Aviva Investors chief executive in 2014, sounded the warning on the UK’s 2011 auto-enrolment reform. Since then, around 10 million predominantly low-paid workers have been automatically enrolled in pension schemes for the first time.