Two former ministers yesterday voiced their alarm at a ‘cynical’ US investment firm targeting Aviva’s army of private investors and trying to buy their stock on the cheap.

The criticism from Ros Altmann, a former pensions minister, and John Glen, an ex-Treasury minister, will pile pressure on the Financial Conduct Authority (FCA) to act.

FCA chief executive Nikhil Rathi is likely to be questioned over the ‘scam’, uncovered this week by the Daily Mail, when he appears before MPs on the Treasury select committee – of which Glen is a member – today.

The uproar centres on US firm Litani, which has written to 100,000 of Aviva’s retail investors seeking to buy their shares for £5.30, well below their closing price of £6.61 yesterday. Aviva has in turn written to them to warn against accepting.

Altmann said: ‘My blood is boiling. It is a cynical attempt to exploit the vulnerable shareholders, who will most likely be elderly, who could be bamboozled by the technical terms being used and the way it’s being presented to them and not understand what’s going on.