David Cameron today warned that the health and future of British politics was in a "dangerous" state because of the huge damage caused by the Westminster expenses crisis.
The Tory leader said British politics had become "reviled" because of the scandal and was now facing a critical moment.
If all political parties did not urgently rebuilt public faith in parliament, it would "descend further into a state of ridicule and contempt", Cameron said.
In a keynote speech to the Scottish Tories' annual conference in Perth today, he revealed Tory MPs would this weekend stage public meetings with constituents to address their complaints, while their expenses would be published online from today.
The UK's political system had "lost the trust of the people", he said.
In Scotland, the crisis could be exploited by the Scottish National party to increase distrust in the union and Westminster and promote independence from the UK, he added.
After recapping the stringent controls on claims he had ordered his MPs to observe, he said these unilateral measures would not on their own repair the deep damage caused by the scandal.
"I understand how deep the damage goes. Our politics are reviled. Our parliament is held in scorn. Our people have had enough," he said.
"Let us be clear. This moment is dangerous, yet vital. The decisions we make and the actions we take in these coming days, weeks and months will help determine the future path of our politics and of our parliament.
"Will it be the politics of change and hope – or the politics of distrust and despair?
"We will need to make big changes to fix our broken politics ... future generations will not forgive us if we take the wrong path."
Cameron confirmed that he would throw out any Tory MP who refused to submit to his party's new scrutiny panel inquiries into their expenses, earning loud applause from the capacity audience.
Tory MPs would be told to pay capital gains tax if they sold a house funded by taxpayers and they were now banned from claiming the costs of furniture, household goods, food and decorations.
As for "flipping" second homes, Cameron said: "I've flipping banned it."
"Too many MPs, from all parties, have made expense claims that do not stand up to public scrutiny," he added.
He said many MPs had forgotten that they worked for the voters and were paid by them. "That's why I'm pleased that some of my colleagues who have been in the spotlight this week are going straight back to the people who put them in parliament," he told the audience.
"They are holding open public meetings in their constituencies."