Fewer than half of FTSE 100 <.FTSE> companies publish staff turnover in their annual reports, and only 11 per cent break down their staff by full-time, part-time or temporary workers, the Pensions and Lifetime Savings Association said.

"The management and engagement of the workforce can have a material effect on a company's performance over the long term," the PLSA said in a statement, adding the letter was supported by pensions minister Richard Harrington, and fund firms Newton Investment Management and USS Investment Management.

British lawmakers are looking into executive pay and corporate governance after Prime Minister Theresa May has denounced as irrational and unhealthy the yawning gap between the amounts paid to bosses and those paid to the average worker.

Funds trade body the Investment Association last week asked FTSE 350 companies to disclose pay ratios between the CEO and the median employee salary and to provide investors with greater context to understand the scale of pay and bonuses.

FTSE 100 firm Sports Direct's working practices have been criticised by politicians who compared conditions at the firm's warehouse in central England to a Victorian workhouse.

(Reporting by Carolyn Cohn)