David Cameron's former chief strategist has launched a bruising attack on the "insular ruling class" who control Britain.
Steve Hilton said too many of the people who make decisions go to the "same dinner parties" and send their children to the same schools.
Complaining that governments act for the rich rather than the poor, he said democracy is in "crisis" because whatever the result of elections the same group stays in charge.
"Our democracies are increasingly captured by a ruling class that seeks to perpetuate its privileges," Mr Hilton wrote in an article for the Sunday Times.
"Regardless of who's in office, the same people are in power. It is a democracy in name only, operating on behalf of a tiny elite no matter the electoral outcome."
Mr Hilton - who left Downing Street in 2012 to teach in California, but remains close to Mr Cameron - suggested the fundamental problem had helped fuel the rise of the SNP in Scotland and Ukip in England.
The intervention, part of a promotional drive for his new book on democracy, is likely to be seen as a rebuke to the Prime Minister. Mr Cameron has long been criticised for surrounding himself with fellow Old Etonians and Oxford contemporaries.
Decrying the influence of big donors on the political system, Mr Hilton said: "We have, in some ways, regressed. Corruption used to be the norm in countries, democratic or otherwise. Power was inherited and bought; political appointments were traded for favours in a system under which the elites literally owned the state.
"While it is no longer so explicit, in the capitals of western democracies the ascent of big money and its lobbyists means that, while there is no explicit quid pro quo, it is hard to mistake what donors intend when they give money to political parties and campaigns.
"Or what business people want when they take politicians and civil servants to dinner, the opera, the Brits, Wimbledon.
"We no longer have aristocratic courts and inherited offices, but our democracies are increasingly captured by a ruling class that seeks to perpetuate its privileges."
While in America power was dispersed, the centralised nature of the UK was a "gift to the vested interests".
"When the corporate bosses, the MPs, the journalists - and the authors of books such as mine - all go to the same dinner parties and social events, all live near one another, all send their children to the same schools (from which they themselves mainly came), an insular ruling class develops," he said.
"They flit and float between Westminster, Whitehall and the City; regardless of who's in office, the same people are in power. It is a democracy in name only, operating on behalf of a tiny elite no matter the electoral outcome. I know because I was part of it.
"While there is no conspiracy (and I know from personal experience that almost all politicians and officials have good intentions), the assumptions, the structures, the rules that govern our lives are not subject to anything as unpredictable as the will of the people.
"No wonder voters feel that others' voices are being heard more than their own. It's because it's true."
He added: 'From the rise of the Tea Party and Occupy movements to the protest parties in Europe, Ukip and the nearly successful vote for Scottish independence, it's clear that our political systems - in the UK, America and continental Europe - are not translating people's wishes into action.
"We need to change that: we need to make democracy work as it was intended to, as a vehicle for real people power, not the plutocrat power we have today."