Norway's $1tn sovereign wealth fund, the world's biggest investor in equities, has told UK regulators that company bosses should have to hold onto their shares for at least five years — and possibly longer.

At the behest of the government, the Financial Reporting Council, which is the UK's corporate governance watchdog, began reviewing its influential guidebook on company rules in December. Among other changes, it suggested the minimum holding periods for executives' share awards should be lengthened from three years to five years.