A second attempt to have Prince Andrew testify on oath about his alleged contact with a woman who claims she was an underage 'sex slave' has failed.

Lawyers for Virginia Roberts, who claims she had sex three times with the Duke of York when she was 17, tried to serve papers on him via the British Embassy in Washington but they were returned to sender.

The fifth in line to the throne emphatically denies the American woman’s claims.

Last week, the Mirror revealed the initial letter sent to Buckingham Palace asking for the Duke to make a statement under oath was not accepted.

Instead, it was sent back by couriers FedEx.

The second legal letter states: "This is a formal request to interview you under oath at a time and place of your choosing."

But the Foreign Office has also refused to accept the letter, stating that sending legal papers to a British Embassy was not the 'appropriate way' for them to be served.

Roberts' lawyer Jack Scarola confirmed the second failure.

The Foreign Office added in a statement: "Documents were incorrectly sent to our embassy in Washington."

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"As they were not served via the appropriate channels, we are returning the documents so they can be sent by the agreed international channels for the transmission of legal papers."

Roberts, now a mum of three, claims she was paid £10,000 by Andrew’s billionaire paedophile pal Jeffrey Epstein to have sex with the royal while in London.

In her statements to a Florida court she alleges it was one of three occasions she was 'forced' to be with Andrew three times in 2001 when she was a teenager.

The other two occasions took place in the convicted financier’s home in New York and at an underage orgy while on his private island in the Caribbean.

Last week, at the World Economic Forum in Davos, the Duke broke his silence over the scandal saying he wanted to “reiterate and reaffirm” Buckingham Palace statements dismissing the accusations.

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Roberts has vowed to “pursue all reasonable and legitimate means to have criminal charges” brought against Epstein, Andrew and "powerful people”.

The rejection of the letters could led Roberts' legal team to pursue Prince Andrew through the British courts under an international treaty.

Under a 1970 Hague convention, to which the US and the UK are both signatories, the lawyers could ask the British courts to question him, through a "letter of request".

Roberts claims against the Duke of York - nicknamed 'Air Miles Andy' for his love of flying - came after she joined three other women as part of lawsuit against US prosecutors.

The Prince is not a party in their claims.

Jeffrey Epstein
Links: Prince Andrew remained friends with paedophile Jeffrey Epstein despite his conviction

The victims claim federal attorney’s broke the law by failing to consult them before signing off on a plea deal.

Lawyers have described the arrangement as a “sweetheart deal” achieved by Epstein and his high-powered legal team after they put pressure on prosecutors.

Without a plea bargain, he would have faced sentences up to 20 years in prison.

Last year the two original claimants, Jane Doe #1 and Jane Doe #2, won a crucial legal victory in being granted permission to see confidential documents relating to the plea deal.

In the new court papers Roberts claims her contact with Epstein, who was jailed for soliciting a minor for prostitution in 2008, began when she was approached by British socialite Ghislaine Maxwell, the daughter of the late media mogul Robert Maxwell, in 1999.

According to documents she alleges the 54-year-old “was one of the main women whom Epstein, 62, used to procure under-aged girls for sexual activities”.

Maxwell’s lawyers have said that she “denies each and every allegation made by Virginia Roberts”.

Despite Epstein’s conviction and to huge embarrassment of Buckingham Palace it failed to stop the Prince visiting his friend in New York following the disgraced banker’s release from prison.

The pair were spotted strolling through Central Park together sparking anger which eventually led to Andrew stepping down from his role as Britain’s trade envoy.