Suspicious trading ahead of large US mergers and acquisitions has risen four-fold in the past five years, suggesting that the recent M&A boom might have sparked an even bigger increase in insider trading, according to analysis commissioned by the Financial Times.

Almost 60 per cent of the 27 big deals announced in North America so far this year were preceded by unexplained spikes in trading in the stock of the target company, according to a review of data by Measuredmarkets, a Toronto research firm. This compares with 14 per cent for the seven largest deals announced in 2003.