David Cameron has said the government will set out plans to allow private and voluntary groups to run almost every kind of public service.
He told the Daily Telegraph there would be a new "presumption" that private companies, charities and voluntary groups could run public services.
A "complete change" was needed to boost standards and end the "state's monopoly" over public services.
But unions accused him of trying to "privatise everything".
Ministers are due to publish a White Paper outlining the changes in the next fortnight.
In his interview, Mr Cameron promised to release public services from the "grip of state control" as part of his Big Society agenda.
The prime minister said he wanted an automatic right for private sector bodies, charities and voluntary groups to bid for public work.
He also said decision-making power would be given back to professionals and people would have more control over the budget for the service they receive.
Mr Cameron wrote: "We will create a new presumption - backed up by new rights for public service users and a new system of independent adjudication - that public services should be open to a range of providers competing to offer a better service.
"Of course, there are some areas - like national security services or the judiciary - where this wouldn't make sense. But everywhere else should be open to real diversity."
Mr Cameron promised to end the "old-fashioned, top-down, take-what-you're-given" model of public services.
He insisted the state still had a crucial role to play in ensuring fair funding and access.
But General Secretary of the Trades Union Congress Brendan Barber accused Mr Cameron of pursuing a "naked right-wing agenda" that would take the country back to the most divisive years of the 1980s.
"The prime minister has been telling us that the cuts are sadly necessary, not a secret political project to destroy public services. Yet today's proposal to privatise everything that moves is exactly the kind of proposal that voters would reject if put at an election.
"What is particularly laughable is the idea that this will reduce bureaucracy. Privatisation replaces democratic oversight and accountability with a contract culture that is a job creation scheme for lawyers.
"Voters and service users lose their say in what will be a get even richer quicker scheme for the companies that win contracts."
And Rail, Maritime and Transport union leader Bob Crow said the government would "privatise the air that we breathe if they thought they could away with it".
Anticipating criticism in his article, Mr Cameron said: "This is not about destabilising the public services that people rely on; it is about ensuring they are as good as they can be.
"These are practical reforms, driven by a clear rationale that the best way to raise quality and value for money is to allow different providers to offer services in an open and accountable way."