Vocus Group shares have dropped more than 15 per cent after Swedish private equity firm EQT Infrastructure withdrew its $3.3 billion buyout offer.

The owner of the iPrimus and Dodo brands told the market late on Tuesday EQT had withdrawn its offer after a period of due diligence, making it the fourth suitor to drop its bid for Vocus in the past two years.

Shares fell 17.6 per cent soon after the market opened before recovering to $3.88 per share in early trading.

Last week AGL withdrew a non-binding takeover offer for Vocus after failing to agree to due diligence terms with the internet provider.