Hargreaves Lansdown has rebuffed a takeover proposal worth £4.67 billion (€5.48 billion) made by a private equity consortium on 26 April.
On Wednesday, the board of directors said they were unanimously opposed to the offer which values individual shares at 985p, claiming it "substantially undervalues" the business.
The consortium includes buyers CVC Capital Partners, Nordic Capital, and Platinum Ivy, a subsidiary of Abu Dhabi's sovereign wealth fund.
The consortium's offer represents a 30% premium on Hargreaves Lansdown's share price of 755p at the end of April, although the stock's value has since risen.
At around 10h45 CET in daily trading, the share price was up more than 8%.
The private equity group said it was continuing to consider a possible offer for Hargreaves Lansdown and explained that a further announcement would be made. The group of investors must decide whether to make a firm offer by 19 June.
The recent bid is part of a wider trend of private equity firms investing in the UK's wealth management sector.
In February, US-based company Charlesbank Capital Partners became the lead private equity investor in UK-based Perspective Financial Group.
Both Cardale Asset Management and Ascot Lloyd have been acquired by private equity companies in recent years.
