Thames Water has told a court it has tried to address its failings, as the water company faces its biggest ever fine for pouring raw sewage into the River Thames.

The water company admitted a number of charges of unlawful discharge and breaching ammonia levels over a two year period from 2013.

Aylesbury Crown Court previously heard how hundreds of fish and birds had been killed because of ‘out of control’ treatment centres sending untreated water into Oxfordshire and Buckinghamshire rivers.

Defending the firm yesterday, Richard Matthews QC said that £17m had been spent on improving its facilities.

He said: “I’ve not said at all that I’m asking for discount from events in 2013 because of the promises set in 2016.

“I’m setting out a background as to how much has changed, some of it involving painful and difficult employment decisions

“To be fair to the new CEO he comes into a business that’s made up of individuals, many of whom care passionately about the job they do. That needs to be demonstrated that that’s the position and that things have changed since 2012 and 2013.”

More than £5.6 million was spent to improve the sewage treatment plant at Little Marlow, Bucks, £1 million at Henley and a further £323,000 at Didcot.

Mr Matthews added: “In the past month with the new system, there have been nine proactive interventions made preventing a problem before it arises.”

Thames Water has admitted several breaches of Environmental Permits and is due to be sentenced on March 24.