The group has now brought in the consultancy Interbrand to review Beefeater, as David Thomas, Whitbread's chief executive, admitted that converting 36 of the 245 Beefeaters to Out and Out had "not worked to the degree we wanted".
He said: "Beefeater is missing like-for-like sales targets and I believe we can extract a lot more value from this estate. We have introduced a brand review to get the positioning tightly defined."
Thomas said the 1.4% like-for-like sales growth at the Beefeater chain over the previous six months was "frankly not good enough". He said: "We do not expect our investors to keep putting up with excuses. We've put in place a number of actions to address its performance and improve returns.
"This may mean that a number of sites are converted to other brands while a number of under-performing units may be sold."
The Beefeater estate is in the books for around £325m, and Thomas said he was "confident" of book value for any sites sold.
Thomas would not say how many sites may go, but dismissed suggestions that the whole 250-outlet chain would be sold off. He said: "The top Beefeater sites average £23,000 a week and an 18% return on capital, so the potential is there. We feel there is prize within Beefeater that we can extract. It would be crazy not to try to get the best out the chain before more radical action is contemplated."
Thomas said Whitbread had no interest in acquiring Compass's Travelodge and Little Chef businesses. He said the asking price was "a third more for a product that is inferior" to Travel Inn, while "Little Chef is a basket case in all but name".
Instead, Thomas said, he preferred to spend £250m to £300m a year on Whitbread's existing businesses: "Organic growth does sound boring but it's a far better way of creating wealth than splashing out on someone else's assets at a big premium." Thomas said the number of Brewers Fayre restaurants would rise by 250 to 600.
Whitbread reported pre-tax profits for the six months to August 31 that rose from £110.8m to £118.4m, despite turnover falling from £1.08bn to £913.6m.
Whitbread shares rose 40p to 540p, yesterday, still below the net asset value of 661p a share, but David Richardson, Whitbread's finance director, said: "In the long run the market will recognise the value. We've only been around 260 years."