Entain Plc has said an increased offer from MGM Resorts International to acquire the operator for approximately $11bn in shares undervalues the company.
In a statement on the offer, Entain said: "Entain has informed MGMRI that it believes that the proposal significantly undervalues the Company and its prospects.
"The Board has also asked MGMRI to provide additional information in respect of the strategic rationale for a combination of the two companies."
MGM Resorts International is aiming to acquire Entain in an attempt to boost its online gambling service.
Entain, previously known as GVC Holdings, operates several betting-related brands, such as Ladbrokes, Coral and SportingBet.
In 2018, MGM Reorts and Entain partnered to work together in the US sports betting market under the joint name of BetMGM.
The newly created online gaming operator uses Entain’s technology and MGM Resorts’ licenses and brands. It operates in more than 10 states, including Nevada, New Jersey and Indiana, and plans to expand to 20 states over the year.
Should Entain accept the offer, the company would have a significant presence both online and with its land-based properties.
The offer would be similar to Caesars Entertainment’s acquisition of William Hill; the deal was worth $4bn and should be finalized in March.