Insider trading is rife on the London stock market, according to new figures from the City of London watchdog that suggest it has made little progress in stamping out abuse.

Nearly 30 per cent of takeover announcements in 2004 were preceded by share price moves that pointed to likely insider trading, the UK’s Financial Services Authority said on Friday. The FSA revealed that some forms of insider trading appeared to have increased since it took on new powers in 2001. It signalled on Friday that it would toughen its enforcement approach to high-profile wrongdoers.