"Citizen scientists" have been conducting water quality tests in the River Thames since May.

Water companies that pollute the River Thames have “no accountability”, a group of “citizen scientists” who monitor the waterway have said.

The groups, which include Surfers Against Sewage (SAS) and Water Testing River Thames (WTRT), have been testing at 24 sites between Oxford and Teddington, west London, between mid-March and mid-August.

Of the 210 tests carried out, the groups said 47 failed when it came to harmful levels of e-coli or intestinal enterococci.

Thames Water said it was “committed to seeing our waterways thrive” and has been upgrading 250 sites to help prevent overflows.