It is against the constitution for the head of state to be sent a summons in the form of a written threat, and to be made to comply by public pressure

Presidential aides

Presidential aides said an investigating magistrate had acted unconstitutionally in summoning the head of state to testify in court, and described his summons as "a written threat".

Le Parisien newspaper had earlier quoted a judicial source as saying the investigating judge in the case, Eric Halphen, had "sent a court summons by regular post to the Elysee Palace at the end of last week".

Chirac calls Jospin

A statement from the president's office confirmed that Mr Chirac had received the summons.

Strauss-Kahn: Secret video

"He has already commented on this publicly on several occasions and does not have any other information which he did not already give to the French people," the statement said.

Earlier President Chirac held a telephone conversation with Prime Minister Lionel Jospin and asked him to "do everything in his power to ensure that the constitution is respected," aides to the president said.

"It is against the constitution for the head of state to be sent a summons in the form of a written threat, and to be made to comply by public pressure. It is an illegal act," they said.

The two men are expected to run against each other in next year's presidential election.

Observers say Mr Jospin has made no attempt to make political capital out of the RPR's party funding embarrassments, because investigators believe his Socialist Party also acquired funds illicitly.

The scandal helped bring about a split in the Gaullist camp and led Paris voters to abandon their traditional preference for the Right, resulting in a Socialist victory in mayoral elections earlier this month.

Immunity

The scandal took a twist last year with the emergence of a videotaped claim by an RPR official, Jean-Claude Mery, now deceased, that building companies in Paris paid under-the-table fees in return for public housing and school building contracts from city hall.

If he held information likely to clarify this case, the president of the Republic would not have failed to make it available

Presidential statement

Mr Chirac was mayor of Paris from 1977 to 1995, when he resigned to become president, and during this time investigators believe the city hall ran a number of illegal operations to overcome the RPR's chronic shortage of funds.

Mery's videotaped confession alleged that Mr Chirac was fully aware of the corporate "donations" scheme.

Intriguingly, the videotape was in the possession of a former Socialist Finance Minister, Dominique Strauss-Kahn, who had kept its existence hidden for years.

In a television interview in December, Mr Chirac denied any knowledge of illegal fund-raising, though he said it was widely accepted that all parties had resorted to illicit practices to raise money.

The president, who enjoys immunity from prosecution while he is in office, added that he would resist pressure on him to give evidence as a witness in the courts because he was the "guarantor of the independence of justice... I cannot be answerable to a magistrate".