One of the country's biggest water suppliers which dumped tens of millions of litres of sewage into the River Thames was today (February 3) warned by a judge that they will be given "their biggest fine in history."

Hundreds of fish and birds died over a two-year period when "out of control" sewage treatment centres owned by Thames Water, sent untreated water into rivers in Buckinghamshire and Oxfordshire.

Tampons, condoms and sanitary towels were left floating between the banks of one of the world's most famous rivers and forced a crayfish fisherman to lay off his staff for three years.

A farmer was forced to fence off his cattle from the nearest water supply after cows suffered tapeworm and a nine-year-old boy, who had embarked on sailing lessons on the river, was struck down with a severe stomach bug.

Workers at the site in Aylesbury, Bucks, logged the issues which included babies' nappies not being cleaned off and cases of illegal discharge.

One entry in the logbook keeping a record of the errors, branded the lack of action a "failure waiting to happen" after it emerged management did nothing to resolve ongoing problems of sewage discharge into the river.

Other sites at Henley-on-Thames, Didcot, Little Marlow, and Littlemore, suffered failings and contributed to the River Thames, River Wye and The Thame river being polluted with human waste between 2013 and 2014.

Prosecuting Thames Water at Aylesbury Crown Court on behalf of the Environment Agency, Sailesh Mehta, said the sewage treatment works at Aylesbury were designed some time ago but were designed to deal with effluent coming in for 100,000 people.

"If there are bacteria and other organisms and the volume is too high, then that effectively sucks the life and oxygen out of the river.

"Something in the region of 40 to 50 per cent of the flow of the river comes from the sewage works. The higher the percentage of the river flow the more important it is to ensure it is clean.”

A later entry in the logbook stated that the issues had been reported to the line manager but nothing had been done to resolve the problems, adding that it was a "failure waiting to happen."

Fisherman Alan Mitchell lost business in his regular fishing spot for three years and noticed the impact of the pollution for three kilometres downstream.

Mr Mehta revealed that a second site at Little Marlow had anywhere between eight to 32 million litres of waste flowing into "one of the world's most famous rivers" each day while sanitary towels, condoms and tampons were also dumped in the river.

A series of failures and a lack of care and attention at the site led to one worker writing numerous entries complaining about blocked pumps before penning "I resign today."

Levels of ammonia described as being "devastating to life" were detected during tests on the river at a Thames Water site at Henley-on-Thames before 50 dead fish were spotted floating on the surface of the river.

Previous management in Little Marlow had posted a list of do's and don'ts around the sewage treatment plant in 2006 in a bid to keep the troubles under wraps.

Judge Francis Sheridan labelled it a "deplorable document" as Mr Mehta, prosecuting, revealed instructions from the "don'ts" section.

One read: "Don't discuss your views on the cause of the problems with any customer, the Environment Agency or the Press."

A dog walker also saw the river teeming with dead ducks, swans and geese in the autumn of 2012 while a wedding reception was ruined due to the smell of the river, the judge was told.

After hearing of the amount of sanitary towels, condoms and nappies being found in the incoming sewage to the plant, Judge Sheridan suggested the public should take more care rather than treating their toilet as a "dump."

He said: "It's not all down to Thames Water. There's a responsibility for everyone to use sewage system properly."

Thames Water Utilities admitted several charges of unlawful discharge and breaching ammonia levels under the Environmental Permitting Regulations in relation to the five sites and will be sentenced on February 22 by Judge Sheridan, who has revealed he is contemplating awarding compensation to those affected.

After hearing most of the prosecution's case Judge Sheridan said: "This is likely to be the biggest fine Thames Water has ever faced."

The hearing continues.