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Zack Polanski has called for a freeze on the approval of new data centres in England because of concerns about the amount of water and energy they use.
The Green Party leader said the government should introduce stricter environmental rules and give communities more say on whether the centres are built in their area.
Data centres can use significant amounts of water to cool their systems, although there are no official figures on how much water they consume in the UK.
The government said a pause would lead to the UK losing investment and being dependent on overseas computing for sensitive data processing.
A spokesman said: “It would be a disaster for jobs and national security.”
There are hundreds of data centres in the UK – with plans for many more.
Exact numbers are hard to find, but the BBC reported last year there were around 477.
Many are clustered around London and the south of England – areas which are officially in drought at the moment.
The amount of water data centres consume can change based on size, design and local climate – the hotter the area the more water needed to cool the equipment.
Speaking on a visit to the site of a proposed data centre in East London, Polanski told the BBC: “We need to slam the brakes on these energy guzzling, water guzzling data centres.
“Essentially, we need basically a moratorium other than local scale data centres for the local community.
“At a time when three-quarters of the country are in drought, it is outrageous that these are being considered critical infrastructure.
“To most people critical infrastructure means hospitals, water, electricity. It doesn’t mean Artificial Intelligence.”
Data centres were classified as critical in 2024, meaning they get extra government support during incidents like cyber-attacks or extreme weather.
The Greens argue this means they could get priority over households for water. The government said data centres would not automatically get priority during shortages.
Mark Acton, executive director of the Data Centre Alliance, said data centres were not taking water from local communities and used less water than leisure centres and golf courses.
Speaking to the Today programme, he said getting planning permission was “very difficult” even in AI growth zones.
He added: “Data centres are not just AI, data centres run our lives… social media runs through data centres, our banking systems run through data centres.
“We depend on these things massively.”
The BBC has discovered that ministers have not carried out an environmental assessment on the impact of their “Delivering AI growth zones strategy“.
A government official said it sees the paper as a statement of intent, rather than a formal policy moving towards implementation.
Data centres in the UK do not currently have to report the amount of water they use.
The Water Research Centre consultancy estimated in February that centres in England currently use about 1.9bn litres of drinkable water a year – around 0.2% of the non-household market.
The company says there is a “clear upward trend” in the use of water.
The Greens cited research by Global Action Plan, an environmental charity, which suggested large centres could consume 1.5m litres per day.
The party said data centres should be built on brownfield sites, near to renewable energy sources to allow them to use renewables when possible.
The Greens also want owners to provide annual figures on water and electricity consumption.
But the government said much more water – roughly a fifth of the supply – was lost through leaks.
A government spokesperson said: “A pause on building new data centres would simply send investment and good jobs abroad, while leaving Britain dependent on overseas computing for the processing of sensitive health and defence data.
“Put simply: it would be a disaster for jobs and national security.
“That said, this does not mean a blank cheque for Big Tech or that every data centre should be approved.
“Developers must plan to use clean power, use water responsibly, create British jobs and supply chains, and provide investment to the communities in which they are built.”
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