Chirac says he has nothing to hide
Correspondents say this is another setback for the French president who admits paying for holidays with wads of cash but says the banknotes came from a secret but legal fund from his time as prime minister.
The three magistrates have accepted that they do not have the power to summon a sitting president but requested additional details from the national assembly in order to keep the "cash-for tickets" case alive.
"This is an attack on the institutions and functions of the president of the republic," said Nicole Catala, from Chirac's Rally for the Republic party.
This was denied by the Socialist President of the National Assembly, Raymond Forni: "My only guiding line in dealing with this was respect for the rule of law and democracy."
Jacques Chirac is expected to face a strong challenge from Prime Minister Lionel Jospin of the Socialist Party.
Air tickets
On 10 July, the investigating magistrates questioned Mr Chirac's daughter, Claude, about some of the trips.
She is her father's senior public relations advisor.
They want to discover where the French President obtained some FFr2.4m ($312,000) in cash, used to pay for air tickets in the mid-1990s before he became head of state.
The payments were uncovered during investigations into public works contracts during Mr Chirac's 18-year term as Mayor of Paris.
The magistrates had asked the national assembly to disclose whether the cash was listed among his assets when he was a deputy from 1988 to 1993.
Mr Chirac says the banknotes originated from a "special fund" allocated to French Prime Ministers and Presidents.
Backhanders
He was prime minister until 1988 - four years before the first ticket was purchased.
The judges believe the large amounts of cash may have instead come from bribes paid by firms to get contracts from Paris city hall.
During his traditional Bastille Day interview on 14 July, the president said that the sums involved were much less than quoted in the press and that he had paid in cash for reasons of "discretion and security".
He said he was "deeply wounded" by the treatment of his family during the investigations.