Our biggest polluters: Water companies revealed to be worst for incidents which have left England's beaches and rivers no-go areas Largest water companies responsible for 1,000 incidents since 2005 Incidents include sewage pumping into harbours and rivers MPs claim small fines are not spurring companies to act to stop pollution The country's 10 biggest water companies are the biggest polluters of rivers and beaches, it was reported today. But despite the water companies being responsible for more than 1,000 pollution incidents since 2005, they have only been fined £3.5million. Incidents include sewage pumping into harbours and rivers and pollution killing fish and wildlife. Pollution: Many British beaches, including Blackpool, failed to meet the minimum water quality standards set by the EU last summer Offences: The country's 10 biggest water companies were responsible for more than 1,000 pollution incidents since 2005, including into rivers and streams According to the data, obtained by The Observer from the Environment Agency under the Freedom of Information Act, only around a third of incidents led to a fine, with companies being cautioned for the others. The average fine was £10,800 - a pittance in comparison with the £10.5billion customers paid the water companies in 2010-11. An Environment Agency spokesman said pollution could have a 'devastating effect on rivers, beaches, land, wildlife and, in the worst cases, communities'. MPs are concerned the penalties for pollution are too small to encourage the water companies to act to prevent it. Joan Walley MP, chair of the Environmental Audit Committee, told The Observer: 'In law, the "polluter pays" principle is supposed to deter companies from damaging the environment, but in this case the penalties appear to be so pitiful that water companies seem to be accepting them as the price of doing business.' While Simon Hughes MP, deputy leader of the Liberal Democrats, told the newspaper: 'These figures are another indictment of the failings of our privatised water companies in England. Many of them make large profits, pay huge dividends, increase prices and pay little tax. When, in addition, these figures show they don't deliver clean water, the public is entitled to say that our monopoly water providers are neither good corporate citizens nor good stewards of our precious environmental assets.' The Sentencing Council for England and Wales proposed increasing fines depending on the size of the company earlier this year. Its consultation into the level of fines for water companies recommended setting the standard fine for deliberate instances of pollution at £750,000, with the option of changing it for £270,000 to £2million depending on the nature of the offence. Costs: Much of Britain's sewerage system is still based on Victorian infrastructure which takes millions of pounds to maintain But water companies strongly denied they saw fines as a normal part of doing business. United Utilities was the most frequently punished company with 242 offences since 2005, including one fine of £200,000 for 22 incidents of sewage leaking into the River Keekle, in Cumbria. A spokesman for the company said: 'To claim that UU are content to continue to pay fines and accept cautions, rather than improve our performance is completely inaccurate and very damaging. In our case, the number of incidents is declining overall. The number of occasions when we have been fined has dropped since 2005. The instances actually went down year-on-year, five years out of nine. So to suggest we "accept the fine and carry on" is plainly absurd. 'We're not denying we have very occasional problems, and every incident of pollution is one too many for us. But the trend for UU has been one of improvement. Thames Water received the largest fines over the period - a total of £842,500 for 87 incidents. It said it was not in its interests to simply accept fines and cautions and carry on regardless because the cost of clearing up pollution - which is the responsibility of the water companies - can be 'enormous'. Anglian Water was the third most fined company, and its offences included one incident where a works manager ordered the destruction and falsification of records. Fines: Thams Water, whose Mogden sewage works site is pictured, was the most heavily fined company Works: The water companies insist accepting pollution because of small fines is not in their interests as they have to pay for repair and clean-up costs It said it recognised 'there is still more work to do' but added that within the next two years it will have spent £2.3billion on maintaining and upgrading infrastructure, including 40,000 miles of sewerage pipes. A spokesman for Water UK, which represents water companies, said: 'The water industry takes its responsibilities to the natural environment very seriously and any incident that has had a negative impact is deeply regrettable. We never want to see incidents of pollution. The significant environmental and social implications, in addition to the unpredictable burden on resources following an incident, mean it is in no one's interest to pay fines and accept cautions. Water companies invest billions of pounds each year to safeguard the natural environment while providing people with high quality, healthy water to drink and healthy rivers, beaches and bathing waters to enjoy. 'While it's widely accepted there is still room for improvement, there is clear evidence of progress in many areas with the number of pollution incidents reducing year-on-year and growing investment in a number of initiatives to protect and nurture the natural environment.' An Environment Agency worker treats the River Trent at Yoxhall, Staffordshire, after it was contaminated with untreated sewage and cyanide A major river was polluted after poisonous cyanide it contaminated sewage treatment works. Thousands of fish were killed after part-treated sewage, with contained traces of the cyanide, leaked into the River Trent in Staffordshire. The incident began after cyanide entered a sewage treatment works in Stoke-on-Trent through the pipe network. It killed the bacteria used in the sewage treatment process with the result that partially-treated effluent was discharged into the river. This contained 'one part in a million' of cyanide as well as ammonia, said a spokesman for the Environment Agency following the incident three years ago. The public were warned to stay away from the river as officials tried to trace where the cyanide had come from.