Yearly hosepipe bans could become the "new normal" as British summers become hotter and drier, a Thames Water boss warned on Wednesday.
Temperatures are set to hit at least 32C in London this week, prompting the Met Office to issue an "extreme heat" weather warning.
Thames Water strategy and regulatory affairs director Cathryn Ross said the company was anticipating a temporary ban on lawn watering to its 15 million customers in the next couple of weeks.
Ms Ross admitted British households will likely have to cut back significantly on water usage over the coming years due to climate change.
"That is climate change in action and in future we're going to have to look at all the tools in the toolkit to make sure that we keep customers with taps flowing," she told BBC Radio 4.
"It means becoming more water efficient. We use 150 litres per person per day in England, in Germany, it's 120. In Copenhagen where they've had a big push on this it's down to nearly 100 litres per person per day.
"There's loads more we can do."
She added that company bosses are meeting next week to confirm whether they will impose a hosepipe ban in London and the south east, which will see households who use garden sprinklers face a £1,000 fine and prosecution.
It comes as the company faced criticism for losing 600million litres of water a day while paying out millions-of-pounds in staff bonuses and dividends to shareholders.
Thames Water is the worst firm in the country for leaks squandering about a quarter of its supply through burst pipes and spills.
Earlier this week firefighters rescued four people after a water main ruptured in north London.
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The broken pipe in Islington caused floods of up to 4ft and created two sinkholes, damaging 50 properties and closing several roads.
Liberal Democrat Leader Ed Davey said: "People across London and the South East will rightly be furious that Thames Water is losing a quarter of the water it supplies to leaks.
"The public has lost all faith in Thames Water. Their gross negligence to fix these leaks is set to inflict misery on their customers.
Bonuses for water bosses should be banned until these shameful leaks are fixed."
It comes the London Fire Brigade issued a warning about deliberately set grass fires in the capital.
A blaze that engulfed six hectares of land in Feltham last week is believed to have been started on purpose, the brigade said.
Crews have already attended more than 425 grass and open land fires across the capital this year.
The brigade said it is concerned the number of deliberate grass fires could spike further over the summer holidays.
Charlie Pugsley, LFB's assistant commissioner for fire safety, said: "We are still seeing too many fires being started deliberately.
"Whilst the dry and sunny spells of weather will be great for families looking to spend time outside over the summer holidays, it also means that the risk of grass fires is going to increase as the ground becomes drier."
He advised parents to talk to their children about the dangers of playing with fire, to keep matches and lighters out of sight and to get in touch with the Firesetters Intervention Scheme if they have concerns.
It comes as crowds were told not to jump into London's reservoirs and rivers during the heat wave.
Wathamstow Wetlands has warned that there is strictly no swimming allowed in the reservoirs on the 211-hectare nature reserve and people have been told not to jump into Shadwell Basin, a disused dock in Tower Hamlets, to cool off.
A 14-year-old boy died after getting into difficulty in a lake in Cheshunt, Hertfordshire on Tuesday police said.
Officers were called to North Met Lake at 5pm to reports the boy had not resurfaced after jumping into the lake to cool off.
