For the children of Wandsworth, the age of innocence ends this autumn when their council puts a price tag on playtime.

To help fund £55m worth of budget cuts, councillors in the south London borough have decided to charge children £2.50 to use the local playground.

The Tory-run council will pilot the charge at weekends from October at an adventure playground in Battersea Park.

Labour politicians have described the charges as "unbelievably mean-spirited" and an attempt to turn play areas into no-go areas for the poor. An e-petition lodged on the council's website had gathered 154 signatories by Thursday.

The council said the park was "more than just swings and roundabouts" and that because the adventure area contained zip wires and 40ft structures, there were added health and safety staffing costs that needed to be recouped in difficult economic circumstances.

The council also said the charge was being introduced to provide the "best value for money" for local taxpayers.

A survey carried out at the playground by the council revealed that half of the children came from neighbouring boroughs.

"Why should Wandsworth taxpayers subsidise children from other boroughs?" a council spokesperson said.

The borough admits it is not expecting to make much money from the scheme and has no income target in mind but says the playground would have to close if it did not introduce the charge.

"The difficult economic situation we face means we have to consider every aspect of the work we do and the services we provide. The adventure playground is a very popular but also very expensive facility to run.

"Introducing a pilot charging scheme at weekends will allow us to carry on investing in the playground, recoup some of those costs and allow us to continue providing the best value for money we can for our council taxpayers. At around half the price of a child's cinema ticket we do not believe the fee is excessive."

In Wandsworth, band D council tax bills are £687 a year, about half the London average.

Sadiq Khan, the shadow justice minister and Labour MP for Tooting, which is part of Wandsworth, said: "This is unbelievably mean-spirited, even for Wandsworth council. It will be children from the poorest families who lose out.

"As families are squeezed by the Tory-led government's cuts, Wandsworth should be promoting low cost healthy activities, like those on offer at Battersea Park, not driving poorer children and families away."

Ken Livingstone, the Labour candidate for London mayor, said that parks and playgrounds should always remain free. "Only the Conservative party could consider charging kids to play. I believe London's parks and playgrounds should be free for London's families and I am deeply concerned at this attempt to turn publicly funded playgrounds into areas which only the rich and privileged can enjoy."

The council says it will review the charges in the summer of 2012.