Tate Britain has stepped in to prevent the sale of four paintings by Frederick Cayley Robinson.

The gallery made an unusual intervention after University College London Hospital (UCLH) NHS Foundation Trust decided to sell the paintings, which were housed in the main reception of Middlesex Hospital.

The decision to sell was prompted by the sale of the hospital site in June 2006, when the trust decided it had nowhere suitable to relocate the works.

After extensive lobbying by Tate Britain and the Art Fund, the trust decided to withdraw the works from sale the day before they were due to be auctioned at Christie's in November.

The paintings, entitled The Acts of Mercy, depict images of orphans and doctors, and were commissioned and given to Middlesex Hospital by Sir Edmund Davis in 1910.

Tate Britain has offered to store and conserve the works for the next five years, or until the trust can find a suitable space to exhibit them.

Stephen Deuchar, director of Tate Britain, said: "The trust looks to have put plans to dispose on hold, and we hope the paintings can be displayed either at a UCLH building or in another medical context. The trust seems to be happy to look at all the options, if it can find a long-term solution."

But Peter Dixon, the trust's chairman, said that if a solution could not be found within five years, it will revert to an open-market sale.

Deuchar described the paintings as "important works of art", but ruled out an acquisition by the Tate. "We haven't got the funds just sitting around for something like that," he said. "They are not an obvious acquisition for us at the moment."

The paintings are hard to value, he added, but are worth "tens of thousands to millions of pounds", depending on whether they are sold separately or together.

Deuchar also defended the Tate's intervention in the sale. "Tate Britain was set up as the national gallery of British art, and this does imply a particular role in relation to British art," he said.

A spokeswoman for the Art Fund said: "It is unusual for the Tate to take on this role, but it wanted to make sure that the paintings were kept in the public domain."

The trust approached the Tate in 2003, leading to discussions over a long-term loan or transfer, prior to the decision to sell the works.

Patrick Steel