Betting giant William Hill has batted away a revised takeover approach from Rank Group and 888, saying it is "highly opportunistic" and "substantially" undervalues the company.
Online operator 888 and casino giant Rank have tabled an improved proposal of 352 pence per share, compared with their previous offer of 339 pence made last week.
888 and Rank Group have called on the board of William Hill to begin "constructive discussion" in a bid to reach a deal.
Shares in William Hill were down more than 2%.
Gareth Davis, chairman of William Hill, said: "This revised proposal continues to substantially undervalue the company and the cash element of the proposal has not changed. Therefore, the board sees no merit in engaging.
"As we have said before, this is highly opportunistic and complex and does not enhance the strategic positioning of William Hill.
"The board continues to believe we have a strong team to deliver superior value to our shareholders and trading at the start of the second half gives us renewed confidence in our stand-alone strategy."
The fresh proposal would see William Hill shareholders owning 48.8% of BidCo, the company being formed by 888 and Rank Group in order to buy the betting giant .
It would mean William Hill shareholders would take 199 pence in cash and 0.86 of shares in BidCo for each share they own.
The previous deal would have seen William Hill shareholders take 199 pence in cash and 0.725 BidCo shares, with investors holding 44.6% of the combined group.
Rank chief executive Henry Birch said: "With a 48.8% share in the combined business, the largest proportion of the benefits would accrue to William Hill shareholders (as well a significant cash payment), and we hope to engage the William Hill Board in constructive discussions to deliver a deal that makes compelling strategic sense for all three businesses."
888 and Rank Group said the tie-up would deliver cost savings of £100 million per year and would create a the UK's "largest multi-channel gambling operator".
It comes after William Hill said half-year profits were boosted by a strong Euro 2016, helping offset a dire Cheltenham Festival.
Itai Frieberger, 888 chief executive, said: "We are extremely excited by the prospect of creating a dynamic, broad9based, multi-channel gambling business of real scale.
"We expect the combined business to lead innovation in the sector, drive growth and deliver superior returns for all shareholders."