France's interior minister has strongly attacked those he believes are behind a plot to discredit him and prevent a possible presidential bid next year.
Mr Sarkozy's speech was broadcast on national television
Nicolas Sarkozy said he would do everything possible to uncover the truth behind attempts to link him to a corruption scandal dating back to 1991.
Bogus bribery claims were made about the sale of French frigates to Taiwan.
Sarkozy supporters say Prime Minister Dominique de Villepin may have played a part in the smears and should resign.
Mr Sarkozy was speaking in the southern city of Nimes in a wide-ranging address setting out his vision for France.
It is a speech widely seen as heralding a run for the presidency, the BBC's Clive Myrie reports.
The venue was packed with members of Mr Sarkozy's governing centre-right UMP party but it was also carried live on national television.
Mr Sarkozy said there was much that was wrong with the country, like the economy and public services, but he wanted to convince people who were disillusioned and no longer believed in politics to have faith.
"Over recent years, profound virtues of the French people and some of France's secular mainstays have been damaged..." he said
"France has so often been gripped by a fever of destruction."
He focused on some of the issues likely to dominate next year's presidential election, like immigration.
He has advocated tough new rules making it difficult for the families of immigrants already in France to join them from abroad.
The interior minister said he would be tough on crime - another big concern.
He was, our correspondent says, appealing to those who might be tempted to vote for a far-right candidate.
On the alleged smear campaign relating to the Clearstream affair, he said that dirty tricks had "no place" in France and no one should have to face this kind of scandal.
Dominique de Villepin is also said to have presidential hopes
"Politics has been destroyed when you have to defend yourself against shabby put-up jobs organised by agencies seeking to compromise people, and by plotters' apprentices seeking to tarnish people's names," he told the audience.
"Politics of this kind must no longer have any place in our Republic...
"I shall carry through the demand for truth right to the end, because scandals of this nature must never again be seen in the French Republic."
Earlier in Paris, Mr Sarkozy was questioned by judges for two hours as part of a lawsuit he has filed to expose those behind the alleged smears campaign.
"I told them that I want the truth and that I have full confidence in them," he said.
Last week, Mr de Villepin denied newspaper reports that President Jacques Chirac had asked him to have Mr Sarkozy investigated for alleged corruption.