The UK's Financial Services Authority has issued a crackdown on contracts for difference - derivatives that allow for speculation on share price movements - saying it will require investors holding long positions of more than 3% to disclose their positions, despite a backlash from market participants, who say the rules will make the UK less attractive.

The FSA said in July that it would implement a general disclosure regime for long CFD positions, and in a statement this morning said that after "receiving extensive feedback from a broad spectrum of interested parties", the regulator considered the regime "as the most effective way of addressing concerns in relation to voting rights and corporate influence."