David Cameron said Britain faced a broken society and economy
All Conservative MPs' expenses claims will be published online from today, starting with the shadow cabinet, David Cameron has said.
Some MPs caught up in the current row would hold public meetings in their constituencies, the Tory leader told his party's Scottish conference.
Mr Cameron said crucial decisions made in the coming months would determine the future of political life.
Wider change was needed to fix Britain's "broken politics", he added.
Addressing delegates in Perth, Mr Cameron also offered to be grilled by MSPs once a year on any subject if he wins the next election.
As reports on the details of expense claims have continued to dominate the headlines, Mr Cameron reiterated that any Tories who refused to take part in his scrutiny review panel would not be allowed to continue as Conservative MPs.
"All of our MPs, starting with the shadow cabinet, will publish each and every one of their expense claims online for everyone to see - that starts today," he said.
He went on: "Some of my colleagues who have been in the spotlight this week are going back to the people who put them in parliament.
"They are holding open meetings in their constituencies. They will be explaining what they've done, listening to what their constituents think and, together, working out how to put right what's wrong."
Mr Cameron underlined his decision only to allow his MPs to claim the "bare necessities" - not furniture, household bills or food.
He added: "This practice of flipping second homes to get more money - I've flipping banned it."
The Tory leader said: "Our politics is reviled. Our parliament is held in scorn. Our people have had enough.
"Let us be clear - this moment is dangerous, yet vital.
"The decisions we make and the actions we take in the coming days, weeks and months will help determine the future path of our politics and of our government."
Mr Cameron went on to say that, while the political system had lost the trust of the people, social breakdown under Labour had made Britain a grim place for millions to live in, and warned that the union between Scotland and the rest of the UK was in danger.
He said the UK had an economy which was running out of money, with the highest borrowing in peacetime history and the deepest recession since the war.
Mr Cameron said: "The welfare claimant who can work but doesn't work. The father who leaves his family to fend for themselves. The teenager who beats someone up and films it on their mobile phone.
"A battered economy, a broken society - these problems are deep and daunting."
The Tory leader said he wanted to get Britain back on track through core party values, of "thrift in government and responsibility in society".
He praised the work of Conservatives in the Scottish Parliament who, he said, had taken the lead on issues such as tackling drug addiction in deprived communities.
Mr Cameron said he backed devolution "heart and soul", and vowed - as well as his yearly trip to Holyrood - that if he became Prime Minister his Treasury ministers would explain Budget consequences for Scotland to MSPs in person.
And his Scottish Secretary would meet the first minister every month.
Turning to the SNP, Mr Cameron said: "Let me send a very clear message to Alex Salmond.
"I know you've got a plan. I know you think a Conservative government in Westminster will ignore what Scotland wants and needs and that you will use that to promote your separatist agenda. Well, think again.
"Whatever the outcome in Scotland of the next General Election, a Conservative government will govern the whole of the United Kingdom, including Scotland, with respect."