The proposed deal will include an initial £1.5bn payment from senior creditors, with the capacity for a further £1.5bn split across two tranches.
However, Chris Weston, chief executive of Thames, stressed that the investment from creditors would not derail its separate equity-raising process, which is being led by bankers at Rothschild.
He said last week: “The liquidity extension acts like a bridge that enables us to carry on discussing with both potential providers of equity and also our creditors about what Thames’s balance sheet should look like.”
It is understood that the fundraising process has also drawn interest from investment giants Brookfield Infrastructure Partners and Global Infrastructure Partners, as well as Carlyle, the US private equity house, and Castle Water, a supplier backed by the billionaire Pears’ property dynasty.
Industry sources said that private equity firm I Squared Capital had also been approached.
However, Northumbrian, which is not seeking a full takeover bid of Thames, could emerge as a potential frontrunner.
Any investment would serve as a relief for Sir Keir Starmer, who has so far resisted attempts to nationalise Thames Water, which remains burdened by a £16bn debt pile.
The company has been seeking new backers ever since it was abandoned by a consortium of shareholders in April.
At the time, the cast of deep-pocketed investors claimed tough regulatory conditions had rendered the utility company’s business plan “uninvestable”.
CK Infrastructure declined to comment.