Albert II, now 86, finally admitted earlier this year, after a court-ordered DNA test, that Delphine Boël is his daughter.

Mrs Boël has sought for years to have her relationship to the king acknowledged, though has long insisted she was not seeking a title.

However, she has now launched fresh proceedings aimed at allowing her to be referred to as “Her Royal Highness Princess Delphine of Belgium”, The Times reports.

Her lawyer, Marc Uyttendaele, said: “She doesn’t want to be a cut-price child, she wants to have exactly the same privileges, titles and capacities as her brothers and her sister. These are things that belong to her, just as they belong to the other children of King Albert.”