The Tory leader will warn that trust in politics is "draining away" and there has been a "progressive and debilitating alienation" of people from politics. Most voters think politicians are "all the same" and "break promises", he will say.
In a speech to mark the launch of his party's "taskforce on democracy", to be led by the former Chancellor Kenneth Clarke, Mr Cameron will call for fresh ideas to "help restore trust in politics and government".
According to pollsters MORI, only one person in five agrees that the "people in charge know best", with trust in Parliament falling from 54 per cent in 1983 to 14 per cent in 2000. Trust in the civil service has fallen from 46 per cent to 17 per cent.
The Conservative leader will say that in order to rebuild belief in politics "we must stop making incredible promises, and where we agree with our opponents, we should say so. What we've seen in recent years is a progressive and debilitating alienation. Trust in our national institutions is draining away."
The taskforce will look at whether constituencies should be redrawn. But it will not consider electoral reform such as proportional representation.
Mr Cameron will say that people think voting "hardly makes any difference".
"Politicians all seem the same. They break their promises. And in any case, the decisions affecting people's lives are often made somewhere else, by someone else: quangos and bureaucrats. Judges. Europe. Anyone, in fact, other than the local and national politicians that people elect. No wonder electoral turnout is down and support for fringe parties is up."
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