Higher household bills have helped Thames Water return to profit, even as the struggling utility giant saw its debt pile grow to £17.6bn.
Britain's biggest water supplier posted profits of £414m in the six months to September, compared to losses of £149m over the same period last year.
This swing stemmed from revenues rising by 42pc to hit £1.9bn in the first half of the year, prompted by the regulator's decision to approve significant increases in utility bills.
However, despite the improved financial performance, Thames Water admitted it had nearly maxed out a £1.5bn loan facility from creditors, while also highlighting a 5pc increase in debt.
It also warned of an increase in customer complaints owing to higher fees, after Ofwat, the water regulator, allowed Thames Water to increase average bills from £436 to £588.
'Rise in customer complaints'
Chris Weston, the chief executive, said the utility business's financial performance had "improved with strong revenue growth, driven by the regulated price rise".
He said the improvement in its finances had allowed it to spend more on fixing leaks, pollution and water quality, with capital investment up by 22pc to nearly £1.3bn.
He said: "This investment has been funded by higher customer bills, which in turn have led to a rise in customer complaints."
It comes as the company battles to avoid nationalisation, struggling under the weight of its £17.6bn debt pile.
A group of the company's most senior creditors are currently pursuing a potential rescue deal, which is deemed one of the last available routes to stop Thames from entering a taxpayer-backed special administration regime.
Thames said on Wednesday that its reliance on debt had increased over the six-month period.
However, it said it had also increased investment in clearing blockages, relining sewer networks, repairing leaks and installing acoustic sensors.
Mr Weston said: "This progress has all been achieved as we also manage the recapitalisation of the business.
"We continue to work closely with stakeholders to secure a market-led solution that we believe is in the best interests of our customers and the environment.
"This, in turn, will allow the transformation of Thames to continue, a programme that will take at least a decade to complete and will restore the infrastructure and operations of the company."
He added: "The first half of this year has been shaped by good progress across all areas of our operational transformation.
"We saw a 20pc drop in pollution, and leakage performance is holding steady despite the extremely dry summer."