A leading French pharmaceutical firm became a surprise bidder for A.H. Robins Co. yesterday by proposing to buy a controlling interest in the 121-year-old Richmond firm and to fund a $2.475 billion trust for victims of the Dalkon Shield intrauterine contraceptive device.

Robins said it received an oral proposal from Paris-based Sanofi yesterday morning and that the Robins board had instructed management and outside advisers to consider it. Meanwhile, Robins said, it will continue discussions with Rorer Group Inc., a Ft. Washington, Pa., firm that has signed a letter of intent to acquire Robins in a $2.65 billion transaction. That agreement provides for a trust with a $1.75 billion cap on Rorer's liability for Dalkon Shield claimants.

The Rorer proposal is part of Robins' plan for bankruptcy reorganization, which is pending in U.S. District Court in Richmond. But Judge Robert R. Merhige Jr. said last Friday that the sum needed for full compensation of shield victims, over an unspecified "reasonable" period, is $2.475 billion -- the amount accepted by Sanofi in the proposal yesterday.

Sanofi, which has 15,300 employes, produces human and veterinary pharmaceuticals, cosmetics and perfumes, and additives for the dairy and cheese industry. The French oil giant Societe Nationale Elf Aquitaine has a 60 percent stake in the firm.

Earlier yesterday, Merhige gave Robins until Dec. 28 to submit a revised reorganization plan that would include the $2.475 billion.

In a related development, the Dalkon Shield Information Network, a nonprofit support group with more than 1,000 persons on its mailing list, called on Merhige to order the $2.475 billion deposited quickly into a trust fund. Attorneys for Robins have called seven years a "reasonable" time to pay the money into a trust, while claimants and the network call that period unreasonable.

"We've waited long enough," Joanne Ackerman of Allentown, Pa., a claimant and a member of the network, said at a press conference. "What is reasonable? I'm supposed to wait another seven years after what they did to me?" said Ackerman, who became pregnant while using a Dalkon Shield and underwent numerous operations, including a hysterectomy.

Karen M. Hicks, president of the network, called Merhige's estimate "a validation" of their claims, but added: "We are not celebrating. ... We plead for this $2.475 billion now to balance the advantages that A.H. Robins has gained during its Chapter 11 status. Robins is posting record profits in every quarter ... while we talk on the telephone to families who are really bankrupt because they cannot pay their staggering medical bills."

Robins, which sold millions of the defective IUDs worldwide in the 1970s, filed for bankruptcy 28 months ago. It had been flooded with product-liability lawsuits.