Environmental activist and singer Feargal Sharkey and adventurer Bear Grylls were among those planning to join The March for Clean Water, which was backed by groups including Greenpeace, the Wildlife Trusts and British Rowing.

Protesters are demanding reviews of water regulator Ofwat and the Environment Agency along with stricter enforcement for water companies who break existing pollution rules.

River Action said that there were around 15,000 marchers, who were encouraged to wear blue and to bring a sample from a body of water close to their heart.

Many wore elaborate costumes, while others held signs reading "tides not turds", "cut the crap" and "water for life".

The new Labour government last month set out legislation that will give regulators powers to issue harsher penalties, including prison sentences, to polluting water companies and their executives.

"We agree that the system is not working. It is too complicated, too slow and is not delivering for people or the environment," said a spokesperson for Water UK, the industry's trade association.

"We cannot delay upgrading and expanding vital infrastructure any longer and need Ofwat to reconsider its approach," it added.