Thames Water has written to Ofwat, the industry regulator, to ask permission to charge customers an addition one-off fee of about £29 per household.
The money is to cover the costs they have spent on acquiring new land for the construction of the Thames Tideway Tunnel. In a statement, Thames Water said:
"Thames Water has submitted an application to Ofwat, its industry regulator, for an interim adjustment to prices for the current price control period, which runs from April 2010 to March 2015.
"The biggest item of expenditure involved is £273m spent on acquiring land required for the construction of the Thames Tideway Tunnel.
"If approved by Ofwat, the net impact would result in a single, one-off additional cost of about £29 per household in 2014/15, equivalent to nearly £6 per year over the five-year period. "