The parents of Madeleine McCann have said that finding the truth about her disappearance while on holiday in Portugal was "essential", 15 years after the "truly horrific crime".

"This year we mark 15 years since we last saw Madeleine. It feels no harder than any other but no easier either. It's a very long time," Kate and Gerry McCann said in a statement on their website.

Madeleine went missing from Portugal's Praia da Luz seaside resort on 3 May 2007 when she was three years old.

Her disappearance sparked a huge manhunt and an international media frenzy, with photographs of the little girl plastered across billboards and news bulletins.

"Regardless of outcome, Madeleine will always be our daughter and a truly horrific crime has been committed," her parents said.

"It is true though that uncertainty creates weakness; knowledge and certainty give strength, and for this reason our need for answers, for the truth, is essential."

Last month, Portuguese authorities joined German prosecutors in declaring a convicted German rapist the prime suspect in her disappearance.

While Portuguese authorities did not name the suspect, it is understood to be Christian Brueckner, the same person German prosecutors are investigating on suspicion of murdering Madeleine.

Kate and Gerry McCann say that time has not made their ordeal any easier (file image)

"We are grateful for the ongoing work and commitment of the UK, Portuguese and German authorities, as it is this combined police effort which will yield results and bring us those answers," the McCanns said.

Meanwhile, the Daily Mirror newspaper has reported that Brueckner had a parole application rejected in Germany.

According to the newspaper, Brueckner - who was sentenced to a seven-year term for rape in a separate case in 2019 - was denied parole in April due to his "social prognosis".

A spokesperson for the Oldenburg District Court told the paper: "The court ruled there were no grounds for suspending the remainder of the sentence."

Brueckner has reportedly denied any involvement in the McCann case and has not been charged.

Lead German prosecutor Hans Christian Wolters told the newspaper: "His request was rejected on the grounds that he could not be given a positive social prognosis.

"In other words, the court has said it believes that the convict will commit further offences if released."

In July 2013, Scotland Yard launched its own investigation, Operation Grange, into Madeleine's disappearance

Detective Chief Inspector Mark Cranwell from the Metropolitan Police, who leads the operation, said: "Fifteen years on from Madeleine's disappearance in Praia Da Luz our thoughts, as always, are with her family.

"Officers continue to investigate the case and our dedicated team are still working closely with law enforcement colleagues from the Portuguese Policia Judiciaria as well as the German Bundeskriminalamt.

"At this time, the case remains a missing person's inquiry and all involved are committed to doing what we can to find answers."

Additional reporting PA