ANZ offered last month to acquire the 65.8% stake it does not already own in Internet broker E*Trade Australia for around $268 million.

At the time of the announcement, Kerry Roxburgh, chairman, E*Trade Australia, said the bid was in the "best interests of all shareholders and are pleased for shareholders to consider it".

But E*Trade Australia now claims that the recommendation was made in the absence of a superior offer and subject to an independent expert's report.

The broker says an independent expert has concluded that ANZ's A$4.05 per share offer "is neither fair nor reasonable" and has attributed a control value for E*Trade Australia of between $4.22 and $4.74 per share for the business.

In a statement Roxburgh says since ANZ made its cash offer E*Trade Australia shares have consistently traded above A$4.05. The volume weighted average price (VWAP) of stock since the ANZ bid is A$4.19, which is four per cent above the offer price.

Roxburg says E*Trade Australia is well placed to continue to operate as an independent entity. "E*Trade is in a strong position to continue to grow its customer base and market share in the online trading market," he says.

ANZ needs 90% acceptance of its A$280 million offer for E*Trade, which expires on 18 April, but has faced shareholder opposition since disclosing details of its bid last month.

In February boutique fund manager Caledonia Investments spent A$4.2 million to increase its stake in the unit from 9.45% to 10.46%, while Invest4Profit - a share research and advisory firm that claims its subscribers collectively own around 10% of E*Trade Australia - has said that it will tell its members to reject the ANZ deal.

Furthermore, earlier this month Australian broker IWL said it may put forward a rival proposal to ANZ's bid for E*Trade Australia after it acquired a "strategic stake" in the Internet brokerage unit.

IWL chief executive Otto Buttula told Australian reporters the firm would not accept ANZ's $4.05 per share takeover offer and that some of E*Trade's own institutional shareholders have encouraged IWL to make a bid for the business.

But with ANZ's current 34.2% shareholding in the business, no other party could acquire 100% of E*Trade Australia without backing from the bank.