Gonzalez said: "The boys are shocked, not only by the news that we are hiding them away as much as we can, but also by the fact that they have to go to the police station here just to say: 'Yes, we are on vacation, our mother knows where we are'."

She confirmed the boys have been in Madrid since leaving Hong Kong, where their father currently lives, and travelled on Friday to Tarifa, a seaside town in southern Spain, where the family owns a holiday home. She said that the children had been asking for a vacation with their father for a long time and one had been planned.

"They are in permanent contact with their mother," Gonzalez said. "They send and receive messages from her, and have talked to her. She knows where they are and what they are doing. The places they are going to are all family residences."

The attorney also said that the Hong Kong court order that gives Hermansanz custody of the children "isn't valid in Spain", where Rubio, the father, has already launched divorce proceedings.

However, the boys' mother yesterday remained adamant they had been kidnapped. Hermansanz, 48, said that she'd obtained a divorce order in a Hong Kong court in October and won custody of the children. She alleges her ex-husband broke court orders stipulating he must pay maintenance and could not take the boys away without her permission.

"Under the court order my husband can only visit the boys in Hong Kong. But he cannot take them anywhere outside of Hong Kong," Hermansanz said.

"He isn't allowed to take them out of Hong Kong even on a holiday. All this is clear in the court order and it's why I went to the police to say that they had been kidnapped."

The police and Department of Justice are continuing investigations into the case.