The Labour leader of Southwark Council has said that one of his party's flagship election pledges - free swimming and gym access for local residents - could initially be offered on just one day out of seven.
Cllr Peter John announced plans for the free swimming and gym access deal in March, two months before the local elections in May.
The free access deal will eventually include The Castle leisure centre at Elephant & Castle which is due to open in Spring 2015.
This week Cllr John was questioned by members of the cross-party overview & scrutiny committee about how the scheme would be implemented.
He said: "It's starting from a point of looking at comprehensive cover for all people at all times at all centres and trying to estimate the cost of that.
"What we have been talking about is piloting 'free Fridays' to see what the uptake would be of free swims and gyms.
"Fridays are a day on which, historically, our leisure centres have not been over-used and it would be interesting to see what the impact is.
"The advice we've been given is that if you start [the free offer] on a particularly busy day you could bring our leisure centres to a halt.
"We don't want to do that. We want to introduce this in a carefully managed way.
"We are looking at potential costings. We know that a comprehensive commitment is quite expensive – £6 million to £8 million probably.
"It's going to be a question of what we can afford to deliver once we have that pilot of free Fridays."
The council leader said that there would have to be some system to manage demand in the longer term, whatever level of free access is provided.
He continued: "We start from the comprehensive position. No decisions have been taken yet to restrict that.
"I'm not saying that it will end up being completely comprehensive.
"I've always thought it would look something like an entitlement to hours in a week or a month for an individual to use a leisure centre."
Cllr John said that the time entitlement would be "meaningful" and would be "commensurate with a healthy lifestyle".