'Don't swim' warnings in place at nearly all of England's official river bathing sites

She says it could take five years before seeing real differences, but the process has already heightened focus on water quality.

Alison Biddulph explains that the Environment Agency has placed a sonde downstream and tests water quality daily, with the aim of unlocking money and objectives for the water company to focus on.

In Shropshire, three bathing sites were designated: two on the River Severn at Ironbridge and Shrewsbury, and one on the River Teme at Ludlow; all have so far rated 'poor'.

The River Wharfe at Ilkley, designated in 2020, is cited as an important test case; when it rains, there can be tens of thousands of E.coli units per 100ml.

Water companies expressed less enthusiasm about the growing number of monitored bathing sites.

Water Minister Emma Hardy said the new bathing sites will improve monitoring, boost local tourism, and give local swimmers greater confidence.

Campaigners say that designation and the testing regime have become an effective way to spur water companies to reduce sewage spills; one campaigner called it 'bonkers' that turning a polluted river into a swimming site could drive cleanup.

Water quality at coastal locations is generally better than inland rivers, which are often polluted by sewage discharges and agricultural run-off.

To be designated as a bathing site the location must meet criteria including the number of bathers who use the site and whether there are nearby toilet facilities.

The results from the tests are posted on a government website.

There are 13 new additions to bathing sites, six on inland rivers; there are now more than 460 locations being regularly tested by the Environment Agency.

Only the River Stour in Suffolk and the River Thames in Oxfordshire had acceptable water quality levels, while water quality at the 12 others was rated 'poor', with signs advising people not to swim.

Water Minister Emma Hardy announced that six new river bathing sites will be monitored for the first time this summer, including a first location on the River Thames in London.

The River Wharfe at Ilkley in Yorkshire was the first river to be designated as a bathing site in 2020.