Article 67 of the French constitution "ruled out a former head of state being forced to provide testimony on events that took place or were known during his mandate and the exercise of his office," a statement by Chirac's office said.

   

"This position of principle...does not allow President Jacques Chirac to respond favourably to the move by judges d'Huy and Pons," it said, adding that Chirac had written to the two judges in charge of the Clearstream investigation to inform them of his decision.

 

Smear campaign

 

The case focuses on a bogus list that suggested Sarkozy and others held accounts in the Clearstream international central securities depository.

   

Leaked case documents fuelled suspicions that Dominique de Villepin, a close Chirac ally, used his position to order secret probes into the case by the intelligence services to discredit Sarkozy, his rival to represent mainstream conservatives in 2007 presidential elections.

   

Villepin, who went on to become Chirac's prime minister, had denied any wrongdoing, saying he was only doing his duty having alleged malpractice investigated.

 

He also denied Chirac ordered an inquiry into the list. Sarkozy served as interior and briefly as finance minister under Chirac from 2002 until earlier this year.

   

Notes made by a former spy drafted in by Villepin to investigate the Clearstream accounts suggested Chirac had in fact asked for the military intelligence officer to investigate the matter.

   

In Friday's statement, Chirac repeated a denial made in an official statement in April 2006, in which he "categorically denies having asked for the slightest investigation into political personalities that have been mentioned".