London & Valley Water said on Thursday that its plan was the "fastest and most reliable route" to turn around Thames, clean up waterways and rebuild public trust.
Investors said they would inject an initial £5.4bn into the company to shore up its finances and support future investment, but they suggested the cash injection needed to be set against "stretching but achievable and realistic performance targets".
All water companies are subject to performance targets over leaks, pollution incidents and customer satisfaction levels.
London & Valley has argued the current targets in place for the company are unachievable and its current business plan needs to be adjusted in order for Thames to attract future investment, rebuild the company and improve its performance for customers.
But Mike Keil, chief executive of the Consumer Council for Water which represents billpayers said Thames "should not receive special treatment around performance targets at a time when customers are paying more and have a right to expect more for their money".
He said recent customer complaints showed Thames had made "some progress, but remains among the industry's worst performers and is the country's least trusted water company".
"The acid test of this proposed rescue plan is whether it would actually deliver improvements for Thames Water customers, many of whom are fed up with receiving a poor service," he added.
London & Valley said under its proposals no dividends would be paid out to shareholders over the duration of the turnaround plan and that new shareholders would commit not to sell the business prior to March 2030.
Outstanding fines would also be paid, they added.
London & Valley Water said it aimed to reach an agreement with Thames and water industry regulator Ofwat "as quickly as possible this autumn given the urgent need to stabilise Thames Water".