Unsolicited bids are running at their highest level in almost a decade as companies use their cash-rich balance sheets to swallow their weaker counterparts.

Since the beginning of the year, unsolicited bids have accounted for 19 per cent of global mergers and acquisitions, according to data from Dealogic – the highest proportion since 1999.

Investors have been galvanised by a range of attacks in recent weeks, ranging from InBev’s $55bn unsolicited takeover of Anheuser-Busch to Schaeffler’s attempt to win control of Germany’s Continental and WPP’s hostile bid for Taylor Nelson Sofres.

Even Chinese companies, which have traditionally been highly conservative when acquiring foreign companies, are turning hostile, as demonstrated this month by Sinosteel’s $1bn takeover of Midwest, the Australian iron ore producer.

Unsolicited bids are defined as offers with the intent to purchase the target and in the public domain, that have not been agreed and recommended by the target’s board.