The fifth-ranking official of the French Republic, the President of the Constitutional Council, Roland Dumas (75), is embroiled in a scandal that has everything: sex in high places and extravagant gifts between lovers, arms sales, Swiss bank accounts, bribes totalling hundreds of millions of pounds and an oil company with its own intelligence agency.

Mr Dumas, who served as President Mitterrand's foreign minister from 1988 until 1993, is being asked to account for his actions and for the millions of francs that mysteriously passed through his bank account.

L'Express magazine describes Mr Dumas as "a flamboyant lawyer, an unsinkable politician, an art lover . . . a character worthy of a novel". His loyalty to Francois Mitterrand, his personal fortune and his career as a ladies' man are all legend, but it is the latter that may prove his undoing.

Mr Dumas was ordered to appear before the Paris judges Eva Joly and Laurence Vichnievsky on March 18th "to answer claims made against him". The judges intend to place Mr Dumas under investigation for "receipt or aiding and abetting the receipt of embezzled company funds".

His rendezvous with justice has been postponed due to minor surgery, but Mr Dumas's doctors say he will be ready on April 4th.

The chief suspicion hanging over him is that some of the 14 million French francs (about £1.68 million) deposited in his bank account in 1991 and 1992 came from the Ffr59 million in "commissions" paid by the state-owned oil company, Elf Acquitaine, to Mr Dumas's then mistress, Christine Deviers-Joncour. Mr Dumas claims the bank deposits were loose change found lying around his law office.

Since the Dumas scandal broke in late January, a June 1990 photograph of him and Ms Deviers-Joncour at a tennis match has come to symbolise the affair. In the photo, France's then foreign minister is elegant. Ms Deviers-Joncour has the look of a woman with expensive taste. Ms Deviers-Joncour (51) has been jailed at FleuryMerogis prison since last November 7th, while she is investigated for embezzlement and fraud.

In a recent interview with Le Figaro, Mr Dumas described Ms Deviers-Joncour as "a friend with whom I maintained private relations".

He claimed he did not intervene to have her hired by Elf at a monthly salary of Ffr50,000.

This was contradicted by Jeanne-Marie Cardaire, Elf's now retired head of personnel, in her October 10th, 1997 deposition. "I was called in . . . and told Roland Dumas, Minister of Foreign Affairs, wanted Elf to hire Mme Deviers-Joncours," Ms Cardaire said.

By her own admission, Ms Deviers-Joncours's duties at Elf, where she appeared only rarely, were simple: to lobby her lover, the foreign minister who had her hired, so he would accept the sale of six French-built Stealth frigates to Taiwan for Ffr15 billion. With its network of former French espionage agents and an annual slush fund of Ffr800 million, Elf had offered its services to the French company Thomson-CSF, which equipped the frigates built in the Lorient shipyards.

Mr Dumas opposed the sale because he feared it would damage France's relations with China. When questioned by judges, Ms Deviers-Joncour claimed Mr Dumas was not influenced by her. In other words, she was paid Ffr59 million in French taxpayers' money for failing to sway him to approve an arms sale.

In the Figaro interview, Mr Dumas said he continued to oppose the deal, but it was approved by President Mitterrand and then Prime Minister Edith Cresson over his objections and signed in September 1991. The French government paid, legally, Ffr2.5 billion in commissions to obtain the contract, Mr Dumas added.

The Taiwanese government seized on Mr Dumas's statement to stop payment on the Ffr260 million still to be handed over for the frigates. In December 1993, Yin Ching-feng, a Taiwanese naval officer involved in the purchase, was found dead in mysterious circumstances. Le Monde reported rumours that Yin was about to publicise the corruption surrounding the deal.

Despite the fantastic sums of money involved, public interest has focused more on Ms DeviersJoncour's lifestyle. The judges believe Mr Dumas was present at a 1992 meeting about his mistress's purchase - with Elf money - of a 320 sq metre, Ffr17 million Paris apartment. Ms DeviersJoncour shared her booty with another intimate male friend, a St Tropez playboy Gilbert Miara (59), who was arrested and jailed on March 9th. The Elf payments passed through Miara's Swiss bank accounts, and he gave her a Ffr450,000 Flemish tapestry. Ms Deviers-Joncour ran up more than Ffr1 million on her Elf corporate credit card, buying in designer boutiques. Purchases included a Ffr11,000 pair of custom-made Italian shoes from Berluti for Mr Dumas. These revelations have strengthened the disgust of French voters with their politicians. If, as expected, Mr Dumas is placed under investigation in two weeks, he will be under pressure to resign as President of the Constitutional Council, a conclave of "nine wise men" who decide on the legality of laws and elections.

He claims he is the victim of a political conspiracy "to destroy the heritage of Francois Mitterrand". His lawyers are fighting to have Judges Joly and Vichnievsky removed from the case, arguing it should be heard by the Court of Justice of the Republic which handles misdeeds by government ministers in the line of duty.

Central to the Dumas affair is Elf Acquitaine, the French oil company established by Gen de Gaulle in 1962 to console himself for the loss of Algeria. For more than three decades, the company - staffed largely by former military officers and spies - made and broke governments in Africa. The company's accounts are a black hole for French government money, and both left and right have served themselves from its coffers when in office.

From 1976 until 1979, Elf spent Ffr400 million on a "sniffer plane" fraud for oil prospecting. No one ever found out where the funds went. Loik Le FlochPrigent, who was president of Elf between 1989 and 1993 - the years of the Dumas-DeviersJoncour affair - has repeatedly been placed under investigation and spent six months in prison in 1996 for his murky dealings.

Elf appears not to have changed its ways; the former Congolese President Pascal Lissouba accuses it of supporting his rival, Sassou N'Guesso, in their war last year.