Property tycoon Robert Tchenguiz on Thursday moved against short-sellers in pub group Mitchells & Butlers, converting a derivatives holding of almost 26 per cent into shares in order to stop it being lent to those betting on price falls.

The move is the latest effort by an investor to limit short-selling as tumbling share prices lead to widespread claims that shorting is partly to blame. Short-selling – a common hedge fund practice – is already in the cross-hairs of politicians and regulators amid fears that aggressive shorting contributed to the failures of Bear Stearns and Northern Rock.