Australia New Zealand Bank (ANZ) has been forced to extend its $4.05 takeover bid for online broker Etrade Australia (Etrade) to May 4 after a lacklustre response from shareholders.

Australia's third biggest bank said yesterday that shareholders would benefit from more time to consider its offer given the uncertainties and business challenges facing Etrade.

In a letter to shareholders yesterday, ANZ group managing director Brian Hartzer said the recent independent expert's valuation, which valued the shares at between $4.22 and $4.74, was unrealistically high.

"The valuation is highly qualified and stated by Grant Samuel to be subject to considerable uncertainty," he said.

"The valuation is at a substantial premium to all other listed on-line broking companies in Australia and the US on a price to earnings multiple basis."

ANZ launched its bid to buy the remaining two thirds of Etrade it does not already own in November.

It has come under constant pressure, however, and a series of leading shareholders have said it undervalues Etrade.

Technology provider IWL, which holds Etrade shares, announced in March it did not intend to accept ANZ's $4.05 offer and increased its stake in the company with a view to a potential bid of its own.

The bid was also met with resistance by Caledonia Investments - its second biggest shareholder - and share research and advisory group Invest4Profit, whose director Paul Nojin called it highway robbery.

Nojin said he would advise his clients, who he claims own up to 10 per cent of Etrade Australia, to sell at no less than $6.00.

Etrade has said it does not plan to raise its offer.