Homes and businesses affected are having to use bottled water while work continues to fix leaks and repair burst pipes following a thaw in temperatures after last week’s cold weather.
In the Commons, Thames Water was criticised for failing to contact residents and tell them how they could collect bottles of water.
Labour’s Chuka Umunna, who represents Streatham, said he was “astounded” at the lack of a Government statement on the issue, adding that “at the very least” there should be “some kind of public inquiry”.
Raising a point of order, Mr Umunna said: “Over the last few years there have been several major water leaks, burst water mains causing severe disruption to my constituents meaning that they can’t wash, they can’t cook, they can’t do the basic things we take for granted.
“Yesterday over 20,000 homes across London and… many others across the rest of the country were left without water.
“My constituency is served by Thames Water. While the snows, the freeze, the thaw has posed huge challenges, Ofwat this afternoon has said that these companies have fallen far short in forward planning, giving the right support and communication to people.”
Labour colleague Helen Hayes, who represents the neighbouring constituency of Dulwich and West Norwood, told the Commons: “Thousands of my constituents have been without water over the weekend, some since last Thursday.
“During that time they have been unable to contact Thames Water by telephone or via the website and they have not received any information on when supply will be restored or how to obtain bottled water.”
She added: “This is a national crisis in our water industry and it is clear that the industry is not fit for purpose.”
As well as properties in London, thousands of premises in the South East, Wales, Scotland, Ireland, the North West, Yorkshire, the South West and the Midlands have been affected.
