United States President Barack Obama has arrived in the United Kingdom for a three-day visit, making an appeal for Britain to stay in the European Union.In an op-ed published by The Daily Telegraph shortly after his arrival in the British capital on Thursday, Obama said that being inside the EU magnifies Britain`s influence across the world.‘As citizens of the United Kingdom take stock of their relationship with the EU, you should be proud that the EU has helped spread British values and practices - democracy, the rule of law, open markets - across the continent and to its periphery,’ he said.In his article, Obama argued that the UK had benefited from being inside the EU in terms of jobs, trade, financial growth and security.‘This kind of cooperation - from intelligence-sharing and counterterrorism to forging agreements to create jobs and economic growth - will be far more effective if it extends across Europe. Now is a time for friends and allies to stick together,’ he wrote.Obama’s intervention before the forthcoming EU referendum on June 23 was welcomed by supporters of the ‘Remain’ campaign, but those who want to leave the EU accused the American president of hypocrisy, reports Aljazeera.Tory MP Iain Duncan Smith, who campaigns for the UK to leave the EU, accused the Obama of double standards.‘He is asking the British people to accept a situation that he patently would not recommend to the American population,’ he said. ‘I can imagine no circumstances under which he would lobby for the US Supreme Court to be bound by the judgments of a foreign court.’London Mayor and Brexit campaigner Boris Johnson also criticized Obama’s involvement in the debate. Writing in the Sun, he claimed that Obama’s view was ‘a breathtaking example of the principle do-as-I-say-but-not-as-I-do’.However, in his article headlined ‘As your friend, let me say that the EU makes Britain even greater’, Obama acknowledged that "ultimately, the question of whether or not the UK remains a part of the EU is a matter for British voters to decide for yourselves’.But he also said: ‘... the outcome of your decision is a matter of deep interest to the United States’.German Chancellor Angel Merkel, French President Francois Hollande and several Commonwealth leaders have already spoken out against Brexit. During his state visit last year, China`s President Xi Jinping also said Beijing wanted Britain to remain in the EU.During his official visit to the UK, Obama will have lunch with Queen Elizabeth in Windsor Castle on Friday. He will have dinner with the Duke and Duchess of Cambridge on the same day and he will speak at a news conference with Prime Minister David Cameron.