The move represents a setback for well-known fund manager Woodford, who recently listed stakes in four unquoted companies on the Guernsey stock exchange, which is regulated by the International Stock Exchange.

In separate announcements for three of these companies – Benevolent AI, Industrial Heat and Ombu – the International Stock Exchange said trading had been suspended since 18:00 on Thursday evening.

The reasons for the suspension are not yet known.

The listings on the Guernsey Stock Exchange only consist of Woodford’s stakes in the unquoted companies, so the rest of the shares that are held by other investors remain unlisted.

Dealing in Woodford’s fourth stake in Sabina Estates, a property developer in Ibiza, has not been suspended.

Woodford Investment Management took the decision to list the stakes in four unquoted companies after its flagship equity income fund came under pressure to reduce exposure to unlisted companies. This is down to continued outflows from the fund; since the summer of 2017 it has halved in size from £10.7bn to £4.7bn at the end of February.

As the size of the fund has decreased, Woodford has sold down positions in quoted stocks to meet redemptions. This has resulted in the fund’s unlisted exposure accounting for more of the portfolio’s assets, at 12%, which is above the regulator’s 10% limit.