LONDON (AP) _ Christie's, the art auctioneers, said an 1805 painting by Francisco Goya could fetch a record price, and it plans to go ahead with the sale despite a claim by the Spanish government that it owns the portrait.

The auction house said last week it had received a letter from the Spanish ambassador requesting that the portrait of the Marquesa of Santa Cruz be returned.

''We wouldn't be selling it if we were not confident that the owners had a perfect right to sell,'' said Simon Dickinson, Christie's old masters expert.

The painting belongs to a company owned by a family trust of Lord Wimborne, who lives in France. He said the dispute with Spain over his right to the Goya has lasted two years.

Paul Whitfield, Christie's public relations director, said when the Goya is auctioned in London on April 11, it may break the world record auction price for a painting - $10.4 million paid last April by the Getty Museum of Malibu, Calif., for the ''Adoration of the Magi'' by Italian Renaissance artist Andrea Mantegna.

In Spain, an official of the Ministry of Culture, Miguel Satrustegui, was quoted by the Madrid newspaper El Pais as saying that Interpol, the International Police Organization, was seeking to recover the painting on behalf of the Spanish government.

Under Spanish law, any painting exported illegally belongs to the government and must be returned, Satrustegui said. The ministry never gave permission for the Goya to leave the country, he said.

El Pais reported that a case is pending in a Madrid court over the painting.

Mercedes Fernandez-Valdez of Bilbao, who had owned the Goya, Pedro Sagrin Bosch, a businessman living in Argentina who apparently bought it, and Michael Simpson, the London art dealer who sold the painting to Lord Wimborne, were accused of falsifying documents to get the painting out of Spain.

''We are convinced that those who carried out the transaction could not have done it in good faith. All the important museums of the world would understand the illegal situation of the painting,'' Satrustegui said in El Pais.

According to the British owners and their accountant, Geoffrey Grime, the painting was offered in March 1983 to Simpson by Sagrin, who allegedly said that he was owed a political favor and he had decided to make use of it by exporting the Goya, then in Bilbao.

Simpson said he recommended Wimborne buy it for resale.

The purchase price was not disclosed.

Sagrin allegedly traveled with the Goya as hand luggage and presented export documents at Madrid airport which Wimborne said appeared quite genuine when they were inspected in Zurich, Switzerland.

London's Sunday Times reported that Wimborne's company offered the Goya to the Getty Museum, but the museum rejected it because of the controversy.

Wimborne said impson had been questioned by Interpol and Spanish authorities. ''All sorts of claims were made by the Spanish to me in the course of the negotiations,'' Grime said in an interview.

''They started out by saying that the export documents were a 'composition' and that they were made up from two different types of document. That was subsequently dropped, so even their side has been inconsistent in this respect.''

Grime added: ''We have bent over backwards to be helpful - we've answered all their questions. We've met them at a number of different places in Europe.''

Wimborne said he thought Simpson was one of the most respected dealers in the London art market. ''I certainly believe that my name is spotless, and I wish to bring all this out in the open so that it is finally put to bed to our satsifaction,'' Wimborne said. ''By going to auction we believe that we clear our names.''