An argument over four old master paintings has evolved into a public dispute between Spain’s National Heritage agency and Madrid’s Museo Nacional del Prado, the Art Newspaper reports.

Madrid’s new €160 million Museum of Royal Collections is scheduled to open in 2016 and the President of the National Heritage agency José Rodriguez-Spiteri wants to show four of the Prado museum’s top old master paintings in it (see Prado Being Stripped of Bosch and Tintoretto Works? and Bosch Masterpieces Will Stay at the Prado Says Director).

Two of the four paintings—The Garden of Earthly Delights (1503-04) by Hieronymus Bosch and The Descent of Christ From the Cross (1435-38) by Rogier van der Wyden—count among the Prado’s biggest attractions.

80 years ago in the midst of the Spanish Civil War, the National Heritage agency moved the works to the Prado for safekeeping, where they have remained on loan ever since.

According to the New York Times the chairman of the Prado’s board, José Pedro Pérez-Llorca, categorically refused to comply with Rodriguez-Spiteri’s demands: “If he is waiting to have the paintings in his place, he has to wait until hell freezes over,” he said in a public statement.

Attempts by the government to broker a compromise between the two institutions have so far been fruitless. Pérez-Llorca fears that complying to the National Heritage agency’s demands could set a dangerous precedent for the Prado.

“It is not private property; they belong to the public,” he clarified. “To deprive the museum because of a whim would begin the dismantling of the Prado.”

However, the Prado Museum hasn’t proven itself to be the best guardian for some works in the past (see 885 Artworks Missing from Madrid’s Prado Museum and Museo del Prado Responds to Loss of 885 Artworks).