GoCompare has confirmed that it "unanimously and unequivocally" rejected an unsolicited takeover offer by ZPG, the company behind sites including uSwitch and Zoopla, earlier this month.
The price comparison group said the potential deal "fundamentally undervalues GoCompare and does not reflect the strong growth prospects of the company".
It marks the latest unsolicited approach by ZPG this year, according to GoCompare, which said that it received an initial offer that valued the company at 110p per share back in May.
That proposal was also rejected by GoCompare's board on grounds that it "undervalued the business and its prospects".
GoCompare said that the most recent proposal by ZPG offered 110p per share in a combination of cash and shares.
This represented a 16% premium to GoCompare's closing share price of 95p on November 7, and a 3% premium to the three-month volume weighted average share price as of that date, which was one day before the proposal was received.
But GoCompare said it also represented a discount to its closing share price of 110.5p on October 11, which was less than one month before ZPG put forward its proposal.
GoCompare said that it has made "significant progress" in the year since its separation from esure Group, and that the board is "confident" in GoCompare's full-year prospects.
Chairman Sir Peter Wood said: "The board and I are extremely pleased with the transformation of the business that the management team has delivered since the demerger.
"The continuing evolution into an entrepreneurial, innovation-focused technology company which we expect will create significant value for shareholders over the medium term by saving people everywhere time and money.
"ZPG's proposal is highly opportunistic and fundamentally undervalues the company and its prospects."
Speculation over the proposed bid sent GoCompare shares higher by nearly 10% or 9.25p to 102p on Tuesday, as investors reacted to reports of the bid ahead of the company's official confirmation.
GoCompare's market announcement and confirmation of ZPG's proposed offer was released at the end of the trading day.