The rumours began to circulate on Thursday, pushing the company’s share price up 8.33%.
Shares in Whitbread closed up 21.5 pence, or 4.4%, at 506p.
Whitbread has so far declined to comment on the rumours. Industry commentators have pointed out that it is already in a joint venture with Yum Brands for the Pizza Hut business in the United Kingdom, although it is thought that Yum may be looking to break free of the agreement. The company also owns the KFC and Taco Bell brands.
The same commentators have also noted that Whitbread is currently in a ‘buy or be bought’ situation, with companies including Six Continents thought to be considering bids.
On Monday, David Page, the chief executive of PizzaExpress, insisted that there would be no management buy-out at the troubled restaurant group despite a further plunge in its share price.
Page said: "I am not interested in working for venture capitalists. What I shall be doing over the next two years is making the profits grow and turning this business round."