Raw sewage discharges into UK rivers and homes will get worse unless the water regulator Ofwat approves major repairs to pipes, a leading academic has warned.
Reporter Julian O'Halloran was shown the state of London's sewers
Up to 7,000 properties are flooded by sewage every year, and in August thousands of fish were killed by waste pumped into the Thames.
John Reynolds of Portsmouth University told the File On 4 programme that Britain's sewerage system had faced years of neglect and was reaching the end of its useful life.
"We are saving money in this generation, requiring future generations to fund our lack of investment."
Lack of investment
Mr Reynolds, a former water company engineer, has analysed the amount of renovation and maintenance work carried out on the sewerage network during the 15 years since water privatisation.
He warned that at current rates of investment it would take 1,500 years to renovate Britain's underground pipes.
Yet in its last five-year investment period, in 2000, Ofwat had cut investment in the infrastructure by 11%, despite evidence that the system was in decline.
"The pipes will eventually collapse," said Mr Reynolds. "We will eventually have more flooding.
"We have to face the problem of global warming and heavier rainfall. That isn't being done within the sewerage system at present."
Ofwat's chief engineer, Bill Emery, insisted there was no crisis in the sewerage network but said a monitoring system had been put in place to forewarn of collapsing sewers.
He also conceded the need for further investment and predicted price rises of up to 40%.
"It's reasonable to think there will be an increasing investment need over the longer term," he told File On 4.
Heavy storms in August killed thousands of fish when more than 600,000 tonnes of untreated sewage was forced into the River Thames. The sudden downpour meant that London's drainage network could not cope and was overloaded.
But the government has not yet agreed to a £1.5bn interceptor tunnel which both Thames Water and the Environment Agency say is the only way to tackle the capital's drainage problems.
They say work must begin on the 20 mile tunnel immediately as it will take 15 years to build.
However, Environment Minister Elliot Morley told File On 4 that he was looking for a cheaper and faster solution.
"If I can find solutions which are quicker, more cost-effective and less disruptive then I think we should consider that."
Although the scale of sewage pollution at the Thames is huge, similar frequent overflows are damaging the environment in other regions.
File On 4 spoke to a landlady in Market Harborough, Leicestershire, whose town centre pub had suffered serious sewage floods in four of the last six years.
Last summer, the beer barrels in Gill Walker's cellar were damaged and her business lost over £30,000.
She feared the next flood would force her to shut up shop.
Market Harborough high street was flooded repeatedly
"I will be gone. A lifelong ambition will just be thrown away."
Anglian Water had programmed remedial work to address the problem which affects scores of other local shops and businesses. But the £1.8m project was delayed for 18 months, awaiting approval from Ofwat.
This summer Ms Walker's pub was flooded three times.
The regulator keeps a tight rein on approving spending on the sewerage network. Any increased investment is likely to have an impact on household bills.
File on 4 is broadcast on Radio 4 on Tuesday 2 November at 2000 GMT and repeated at 1700 GMT on Sunday 7 November.