A Singapore-registered subsidiary of Ontario Municipal Employees Retirement System, which holds a 31 per cent stake in Thames Water, said in accounts filed on Friday it would make “a full writedown of [its] investment and loan receivable with accrued interest”.

Macquarie sold to Kemble, which is now the ultimate owner of Thames Water. Kemble is owned by some of the biggest pension and sovereign wealth funds in the world, but recently defaulted on debt payments, meaning it is now effectively insolvent. That matters because it was supposed to pump more than £3bn in new money into Thames.

A senior official at the biggest shareholder of Thames Water Utilities Limited stepped down from the board of the struggling company, raising questions about how much longer it can hang on without government help.

Thames Water's non-executive director, Michael McNicholas, who represents Canadian pension fund OMERS on the board, is stepping down immediately, Britain's biggest water utility said on Thursday, as it struggles to secure an equity bailout.

The representative of its largest shareholder, the Canadian pension fund Omers, resigned with immediate effect and other members are expected to follow

Britain's struggling Thames Water investors are expected to quit the board of the nation's biggest water utility company after they refused to inject more than 3 billion pounds ($3.79 billion) of equity,