President of the United States, Barack Obama, has advised the UK to stick with the European Union (EU).
President Obama made the call on Friday during his final trip to Britain as US President.
Earlier in the day, Mr Obama and his wife, Michelle, traveled by helicopter to Windsor Castle for lunch with Queen Elizabeth II, who turned 90 on Thursday, and her husband, Prince Philip, 94.
UK Prime Minister, David Cameron, is hosting Mr Obama, who is on a three-day visit with his wife, Michelle at Downing Street.
BBC says London Mayor, Boris Johnson, called his view hypocritical”, describing the EU system as “alien” to US traditions.
Both leaders are holding talks on the fight against alleged Islamic State and would later be joined by the UK’s home, foreign and defence secretaries, as well as the chancellor.
They are billed to deliberate on the progress being made in combating IS in Iraq and other steps to be taken to tackle the terrorists in Syria.
As they are expected to later hold a joint press conference, the leaders would also discuss the situation in Libya, where the West is considering how to support the newly-established Government of National Accord (GNA) in the battle against IS.