Many Londoners are still without water as Thames Water struggles to restore full service after last week's extreme weather.
The utility company apologised to customers who have had now water for several days now, in particular in the south of the capital.
"The sudden drop in temperature has put pressure on our older cast iron pipes, causing more leaks across our network," Thames Water said.
"We’re doing all we can to get to leaks as quickly as possible to repair them – however, due to the weather and the volume of leaks, we may not be able to do this on our first visit. If we can’t carry out the repair, we’ll make sure the area is safe.
"In addition to this the weather is affecting our contact centre agents and field workers reaching their work locations."
Labour MP for Streatham, Chuka Umunna, has called for a public inquiry into the water problems.
"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," he said in the House of Commons yesterday.
"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."
Ofwat chief executive Rachel Fletcher said: "The ongoing water supply problems affecting the country, most particularly parts of London and the South East of England, have been deeply distressing for all those affected. While the recent severe freeze and thaw have undoubtedly had an impact on pipes and infrastructure, this weather was forecast in advance.
A number of water companies appear to have fallen well short on their forward planning and the quality of support and communication they’ve been providing, leaving some customers high and dry.
"Everyone’s number one priority must be getting the water flowing as quickly as possible and ensuring that all customers – in particular those in vulnerable circumstances – get the support they need. 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."