Prince William appears to endorse Britain remaining in the European Union

A Kensington Palace spokesperson said: 'This speech is not about Europe. He does not mention the word Europe once'

Prince William walks with Foreign Secretary Philip Hammond as he visits the Foreign and Commonwealth Office (Getty)

Kensington Palace has denied that Prince William used a speech at the Foreign Office to endorse the UK’s continued membership of the European Union.

Addressing British diplomats at the Foreign and Commonwealth Office the Duke of Cambridge said that “common action with other nations is essential” in an increasingly turbulent world.

His comments came on the same day that Prime Minister David Cameron began crunch talks at a crucial summit in Brussels to thrash out the draft renegotiation of Britain’s membership of the EU.

However, a spokesperson for Prince William said: "This speech is not about Europe. He does not mention the word Europe once." They added that the timing of the speech was a “complete coincidence” and that the invitation to speak at the inaugural Diplomatic Academy awards came “months ago”.

Speaking to the Foreign Secretary Philip Hammond and recipients of the awards, the Duke of Cambridge said: “For centuries, Britain has been an outward looking nation. Hemmed in by sea, we have always sought to explore what is beyond the horizon. That sense of mission and curiosity is something that I know continues to drive our economy, our cultural and educational exports and our Armed Forces and Diplomatic Service. And wherever we go, we have a long and proud tradition of seeking out allies and partners.

He added: “In an increasingly turbulent world, our ability to unite in common action with other nations is essential. It is the bedrock of our security and prosperity and is central to your work. Right now, the big questions with which you wrestle – in the UN, NATO, the Middle East and elsewhere – are predicated on your commitment to working in partnership with others.

“I know from my own experience how important that is. A subject that is close to my heart, the illegal trade in ivory and rhino horn, cannot be solved without nations working together in new ways.”

The intervention by the duke will draw comparisons with the eve of the Scottish referendum in 2014 in which the Queen asked voters to think very carefully before casting their vote.

The Duke of Cambridge also used the speech to pay tribute to his grandmother where he also highlighted how "extremely well" the department handled the Tunisia terrorist attack last year.

At the FCO headquarters in Whitehall, the Duke presented awards to embassy staff from across the globe that have shown leadership, creativity and innovation, and other attributes when supporting the learning of others at the department's Diplomatic Academy.

The institution was opened last year and provides career development training for FCO staff who want to gain greater knowledge about topics ranging from economics to defence and security.

Additional reporting by Press Association