An American private equity billionaire is trucking up to 13,000 gallons of water daily to his country estate in Wiltshire – despite a ban on tankers filling up from nearby mains.

Blackstone boss Stephen Schwarzman, 79, who is one of Wall Street's most powerful financiers, has infuriated neighbours of Conholt Park, near Andover, who face hosepipe bans following the warmest spring on record and a drought.

Last year, the estate admitted using a 'small proportion' of water supplied by tankers to fill an ornamental lake – a move that led Southern Water to ban the delivery companies involved from tapping into its standpipes.

Although the lake is full, tankered water from an unknown source is now being used to water newly planted trees in the 2,100-acre grounds.

While there is no suggestion that this is unlawful, neighbours say it runs against the spirit of national appeals for water to be used wisely.

The estate is supplied by Wessex Water and is not under a hosepipe ban. But it falls within the southern England drought area identified by the Environment Agency last week.

Steve Kershaw, 68, who has lived in the nearby village of Tangley for 40 years, told The Mail on Sunday: 'This is causing uproar. The standing joke is that Lord Lake, as he's known round here, is at it again.'

He added that the estate's grounds were 'a lot greener than people's lawns, which are bleached'.

Another resident said: 'Water companies have started ringing locals warning that they've been reported for using a hosepipe on their garden.

I wonder if they've rung Mr Schwarzman to ask where his tanker-loads of water are coming from, and where it's all going?

'If he needs water, why can't he use some of the nine million litres he's poured into his lake?'

However, other neighbours praised Mr Schwarzman – who has a fortune of £30billion and bought Conholt Park for £82million four years ago – for creating jobs, engaging with local councils and planting trees.

A source close to him said: 'Steve is ensuring that local water resources are not affected.' 

Another source said: 'All water brought to the estate is supplied through licensed providers and sourced lawfully.'

The tanker firm Greens H20, whose 30,000-litre trucks have been seen making daily deliveries to Conholt, did not respond to a request for comment.