Isle of Wight Council bosses have overturned a vote by councillors - who had rejected the partnership to secure £900 million of funding.
New Portsmouth-Based Carrier Will Be Brought Into Service
The second of the Royal Navy's next generation aircraft carriers is to be brought into service rather than sold off, David Cameron has said.
The announcement about the fate of the 65,000 ton HMS Prince Of Wales was made as the 28 Nato members agreed a pledge to maintain spending on defence.
The Prime Minister said the move was an "investment in British security'', and would ensure there was always one carrier available.
HMS Prince of Wales was built along with HMS Queen Elizabeth in a £6.2 billion project. They will both be based in Portsmouth.
But while the latter was always intended for use by the Navy, doubts had been raised over whether HMS Prince Of Wales would be disposed of or even mothballed as part of efforts to rein in the defence budget.
A final decision had not been expected until after the general election.
However, Mr Cameron told a press conference at the end of the Nato summit in south Wales:
"Our brand new aircraft carrier - HMS Queen Elizabeth - was named by Her Majesty in July and has now left her dry dock and is being fitted with her combat systems.
"She will be the mightiest ship the Royal Navy has ever put to sea, able to protect and project our interests across the globe for decades to come.
"And today I can announce that the second carrier - HMS Prince Of Wales - will also be brought into service.
"This will ensure that we will always have one carrier available, 100% of the time.
"They are an investment in British security, British prosperity and our place in the world, transforming our ability to project power globally whether independently or with our allies.''
Admiral Sir George Zambellas, the First Sea Lord, previously upped the pressure on the Government by arguing Britain's credibility "hinges on a carrier being available when the need arises''.
"Hope is not a reliable method of ensuring capability availability when a crisis erupts,'' he said.
"That is why we need the effects of a UK carrier. It's the wrong moment to find out that nothing happens when you push the carrier button.
"So to ensure continuous carrier availability, that means having two carriers, not one.''
Sir George said the cost was "a modest extra premium to pay, for an effective, a credible, an available, insurance policy''.
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