Campaigners gathered in central London to protest against Thames Water seeking High Court approval for a £3billion loan.
The water company says it will go bust by March if it is unable to raise the massive sum.
But analysis from campaign group We Own It found if the bailout is granted it will cost the average person who uses Thames Water £250 more a year.
Thames Water said the loan is the first step of the bailout process needed to avoid running out of cash in the spring at the Royal Courts of Justice today.
The first step has now been granted, meaning a full hearing will be heard and a final decision made in February.
A letter from Windrush Against Sewage Pollution was delivered to the judge hearing Thames’s application by Charlie Maynard, the MP for Witney.
It calls for the court to hear submissions from the public on the bailout.
Ash Smith, Founder of Windrush Against Sewage Pollution, told Metro at the protest: ‘This is frankly a disgrace. We need to be heard. It is about to get very serious for the billpayer.
‘We are already funding a massive amount of debt just to fund Thames Water’s previous unnecessary debts and that could go up hugely.
‘We are concerned that this bailout is not only going to be a massive burden on the billpayer, it is going to become a financial scam.
‘The billpayer is the creditor in waiting. It is already a scandal and could easily be stopped by government.’
Latest London news
To get the latest news from the capital visit Metro’s London news hub.
The regulator Ofwat is also set to decide on December 19 how much water providers can increase bills over the next five years.
Thames Water has reported that there were 359 category one to three pollution incidents in the six months to September 30, an increase of 40%.
Many water companies are under pressure for polluting waterways through not investing in correct infrastructure.
Matthew Topham, Lead Campaigner at We Own It, suggested how the government could help.
He told Metro: ‘The government could use a power used by Blair in 2002 with privatised rail track and put Thames Water into special administration, revoking its licence and bringing it into public ownership.
‘This will also cut the debts that the company has, making it cheaper for the public to invest going forward.’
In response to this, a spokesperson for the Department for Environmental and Rural Affairs (Defra), said: ‘We are closely monitoring the situation and it would be inappropriate to comment on ongoing legal proceedings.’
Professor Ewan McGaughey, professor of Law at King’s College London, told Metro: ‘I think the argument the campaigners are making is a good one.
‘They are saying that the court case could increase Thames Water customers’ water bills.
‘Thames Water want to take on a £3billion loan, paying back £800million in lawyer’s fees and in interest. That is a pretty bad loan.’
A Thames Water spokesperson told Metro: ‘The board and leadership team remain focused on turning round the business and continue to believe a market-led solution is the best financial and operational outcome for customers, the environment, UK taxpayers and the UK economy.
‘We have a robust plan that we are confident delivers on this objective, and this court process is an important step on the path to putting the company back on a stable financial footing.’
The government has confirmed that water companies will pay higher compensation for people impacted by water failures.
People with problems like low water pressure could receive payments of up to £250, compared to the £25 available now.
Meanwhile those impacted by flooding inside their homes from sewers could receive £2,000 or more, compared to £1,000 under current rules.
Get in touch with our news team by emailing us at webnews@metro.co.uk.
For more stories like this, check our news page.
MORE: Farage travels 4,423 miles from constituency to meet with Elon Musk
MORE: ‘Dangerous’ criminal accidentally released from prison the day he arrived
MORE: Plan to move pedestrian crossing 50 yards set to cost £650,000