Michael Roberts, chief executive of Water UK, added: "The recent severe weather has meant there have been multiple burst pipes and leakages across networks".
Up to 13,000 homes across Kent and Sussex have no water - with more people in surrounding areas facing low water pressure.
At a supermarket in Balham, south London, Thames Water employees distributed crates of bottled water to a waiting queue of people, while in Hampstead to the north of the capital, they ferried crates to residential streets in their own cars.
Water suppliers have been criticized for not planning ahead properly, with London Mayor Sadiq Khan saying the shortage is "unacceptable".
Ms Fletcher added that while the current priority was supporting all those affected, further action would be taken once the water is flowing once more. "When the taps are back on, we will take a long, hard look at what has happened here and we won't hesitate to intervene if we find that companies have not had the right structures and mechanisms in place to be resilient enough".
However, some suppliers have kept warnings in place and are advising customers to use water sparingly, as some parts of the United Kingdom are still experiencing shortages.
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"We're sorry to all those customers who are without water".
Speaking at the Water UK City conference, he said that water companies had not been acting "sufficiently in the public interest" and accused some companies of "playing the system for the benefit of wealthy managers and owners, at the expense of consumers and the environment".
The water companies say they are "working hard to prioritize supplies for vulnerable customers, to provide bottled water where necessary". Companies throughout the United Kingdom are warning of low pressure as they try to refill pipes that have lost water due to leakage.
In central England, water supplier Severn Trent said the number of burst pipes was up 4000 per cent, while in Wales, Welsh Water said "unprecedented challenges" had affected 4,500 homes.
The cold weather was blamed on the "Beast from the East" storm that caused temperatures to plunge for days across much of Europe and brought feet of snow to some areas.
The British Meteorological Office (Met Office) noted that the country faces the coldest winter since 1991.