National Grid (LON:NG) selling more of the UK gas transmission and metering grid to Australia's Macquarie is "disastrous for energy security, consumers [and] employees", according to the GMB trade union.
The FTSE 100 listed former government monopoly said it has shaken hands on a deal to further sell half of its remaining 40% stake in National Gas for £700mln.
Assuming the deal is approved - which is not a given - Macquarie and British Columbia Investment Management Corporation (BCIMC) will take their stake from the 60% they currently own following a £4.2bn purchase agreed last year to 80%, with an option to lift this to 100% next year.
Gary Carter, GMB national officer, said: “Macquarie's stranglehold on gas transmission and distribution should send alarm bells ringing.
“Leaving the nation’s gas assets in the hands of Australian-owned private equity is disastrous for energy security, consumers or employees."
Backing up his argument, he noted that under Macquarie's ownership Thames Water debts mushroomed and "brought it to the edge of collapse", with borrowings at the water company having risen from £3.2bn to almost £11bn under its years of ownership between 2006 and 2017 and are now one its "significant issues to address" according to regulators.
The Australian infrastructure investor also owns Southern Water, he noted, which has repeatedly been fined for dumping sewage in rivers and seas in the south-east England.
"It is also the owner of Cadent Gas which makes massive profits - £950mln last year - and paid £350mln in dividends whilst looking to close employees' pension scheme.
"The UK's energy and water companies are not safe under the stewardship of private equity which only sees the UK's assets as a cash cow for foreign shareholders,” Carter said.