Londoners could find their water bills rise by as much as £65 a year to pay for Thames Water’s 21-mile super sewer.

But residents close to proposed sewer entrance site Barn Elms said the true cost of plans to communities could be much more.

Sian Baxter, chairwoman for campaign group Stop the Shaft, which is trying to prevent construction work on the greenfield sports site on the border of Barnes and Putney, said: “If this project goes ahead at Barn Elms the cost to the community will be considerably more than an increase in everyone’s water rates bill.

“Barn Elms playing fields is used by schools from five London boroughs as well as many different sports and social clubs.

“The fields, adjacent tow path and river are the green sporting hub of London and the proposed tunnel construction works will render large parts of it unusable for [about] seven years. ”

Thames Water, which is constructing the tunnel, need to build drive shaft entrance sites along the Thames banks in order to allow access for tunnel drilling equipment.

Barn Elms has been listed as a potential site and, if chosen, residents could face construction work 24 hours a day, seven days a week, for more than three years. This led to the proposal attracting the most comments for any one site in a recent consultation about the sewer build.

Since the consultation Thames Water has announced a possible alternative site south of Carnwath Road, Fulham.

The cost of the sewer build has been suggested to be as high as £3.6bn and the bulk of this will be footed by London residents through their monthly water bills.

Thames Water said regulators Ofwat set the level at which bills are charged every four years. The next time regulation is due to happen is 2015 - which is when any extra costs would come into effect.

A spokeswoman for the water company said: “It is undeniable that our 13.8m wastewater customers will face higher bills to pay for the Thames Tunnel, in the same way that people in south west England, for example, have paid for improvements to sewage treatment works in the interests of cleaner beaches, at a much higher cost per head.

“In September 2010 the new coalition Government asked us to progress the Thames Tunnel. They also announced the projected cost for the project was £3.6bn.

“This would result in the average bill increasing by slightly more than £1 a week by 2018.”