The High Court ruled that privately-owned Thames was entitled to the loan worth up to pound3 billion ($3.9 billion) as it seeks to avoid temporary renationalisation.

However, some of the company's smaller creditors, along with a British politician, are demanding that the Court of Appeal in London overturns the ruling, with the MP arguing that customers would face further increases to bills.

The dissatisfied creditors meanwhile argue that the terms of the fresh loan puts them at a disadvantage regarding repayments.

"Today I am fighting for the 16 million customers who have been left to foot the bill of Thames Water's mismanagement," said Charlie Maynard, MP for Britain's third-biggest party, the Liberal Democrats.

Maynard called for Thames to be put into Special Administration, or temporary nationalisation.

This would allow "much of the debt" to be scrapped, allowing "the company put onto a stable financial footing", he argued.

Ahead of the court hearing, set to last until Thursday, a Thames Water spokesperson told AFP the new loan is "better than any other alternative course of action and we do not believe that the grounds for appeal meet the required thresholds".

The loan is seen as only a short-term solution to keeping afloat the company, which already had pound16 billion worth of debt.

Thames Water is owned by a consortium of shareholders, including Canada's Ontario Municipal Employees Retirement System and the British Universities Superannuation Scheme.

Thames Water, which serves homes and businesses in London and elsewhere in southern England, has separately appealed to Britain's water regulator to be allowed to hike bills more than granted.

Thames customers are set to see average annual water bills rise to pound588 by 2030 following a decision by British regulator Ofwat -- falling short of the 59-percent hike requested by the troubled group.

Thames and other British water companies, privatised since 1989, are also under fire for allowing the discharge of large quantities of sewage into rivers and the sea.

This has been blamed on under-investment in a sewage system that dates back largely to the Victorian era.