Dealmakers and traders were given a stark warning yesterday by the Financial Services Authority (FSA) as it made clear its plans to crack down on insider trading.

The statement came as it was revealed that a quarter of all mergers and acquisitions were subject to the fraudulent activity, following an investigation last month.

The investigation launched by the watchdog was sparked by allegations that rumours were spread to drive down the share price of HBOS. The FSA has faced ongoing criticism and negative comparisons to more stringent US regulators.

The investigation revealed that 28.7 per cent of all takeover announcements last year were preceded by unusual movements in share prices, prompting the regulator to say it wanted to bring back “genuine fear” to the markets.

Teresa La-Thangue, a spokeswoman for the authority, confirmed to M&A Magazine that the FSA would be prosecuting more rule-breakers, who under UK law can face up to seven years in jail and an unlimited fine. The watchdog recently took former General Counsel of TTP Communications Christopher McQuoid and James Melbourne to court, charged with having used inside information. The information related to a proposed cash offer from Motorola for the entire issued share capital of TTP Communications plc.

An FSA spokesperson said: “Clean markets are vital to the continuing success London as an international financial centre. “Market misconduct, particularly in the form of insider dealing and market manipulation is, put simply, cheating and reduces investor confidence in the UK markets.”

Market Abuse Helpline: 020 7066 4900 / market.abuse@fsa.gov.uk