Expert casts doubt on Thames Water super sewer plan
13 December 2012 Last updated at 15:25 GMT
An expert from America who helped solve the sewage problem beneath the streets of Philadelphia has criticised Thames Water's planned super sewer for London.
Dr Mark Maimone, of CDM Smith in Massachusetts, said the company has not properly examined other alternatives before forging ahead with the controversial project.
The sewer tunnel would run from west to east London collecting 39 million tonnes of sewage discharged into the River Thames every year.