It comes as the Conservatives set out their own plans to move power away from the state to citizens and away from government to Parliament.
The proposals are included in the "ethics and accountability" section of the party's draft election manifesto, published earlier on Tuesday.
"Using decentralisation, transparency and accountability we will weaken the old political elites, strengthen the power of the people, fix our broken politics and restore people's faith that if we act together things can change," said Mr Cameron in the document's foreword.
The draft manifesto chapter also confirms that the Conservatives would legislate to stop MPs using parliamentary privilege to evade justice if they won power in this year's general election.
It also includes promises to publish MPs' expenses online, grant electors a power of "recall" to kick out misbehaving MPs, and tougher rules to ban ex-ministers from lobbying government for two years after leaving office.
The Conservative manifesto will also include promises to enhance the status of voters' petitions, making it possible to secure a parliamentary debate by collecting 100,000 signatures, and to table a Bill backed by one million signatures.
The Conservatives will also promise to put limits on ministerial special advisers, cut Westminster perks, reduce the number of MPs by 10% and impose a 5% reduction on ministerial pay followed by a freeze for the rest of the Parliament.
In a foreword to the section, Mr Cameron said that "no-one can doubt that our political system is broken".
"Appalled" voters are "furious and demanding big change" after the expenses scandal, it adds.
Harper has surely destroyed any chance that his Tories may carry a banner of electoral reform into battle, with his obvious contempt for our parliamentary traditions.
This leaves the field open for one or more enterprising opposition parties to run with real reform.