The UK as a country on the world stage is "undoubtedly" on the back foot, the director of an independent international affairs think tank has warned - and the situation could get worse.
Robin Niblett, director of Chatham House, the Royal Institute of International Affairs, said the country was suffering from "an identity crisis", partly driven by its relationship with Europe.
The uncertainty had also "weakened its voice within European circles", he said, and the UK's absence from the Minsk agreement in February, was "symbolic".
Dr Niblett said the issue of the UK potentially holding a referendum on its continued membership of the European Union in the next parliament, if http://www.huffingtonpost.com/news/david-cameron/ won a majority on May 7, was one that was "likely to consume the country" for at least two years after the election.
He said the issue of Europe was consuming a lot of the political debate among the Conservative Party, adding it was "riven again" 25 years after former Tory prime minister John Major saw his party face the same conundrum.
Dr Niblett said the question of Scottish independence, also put the UK on the back foot, while he described Britain as being in an almost "post-Vietnam tired phase" following the interventions in Afghanistan and Iraq.
He said: "There's a loss of political trust of the British people in their leaders on foreign policy, and that's simply compounded by the global financial crisis - but there's also a loss of deeper trust in government competence." Britain's economy, he said, was still a significant factor looking ahead at foreign policy.
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Dr Niblett said: "Any party that wins power is sustaining commitments on social spending, health, education, pensions, where do you make the cuts? You make them in issues like defence, the Foreign Office, potentially even in the future intelligence, which has come out fairly well so far.
"So with the economy in trouble, questions over the public's appetite for intervention and the issues of identity, Scotland, and Europe, I think you see the UK in a tough position - possibly in retreat for a period."
Structurally, Dr Niblett did not think the UK would return to a two-party system for the next 15 to 20 years.
And on UK-US relations under the coalition, he said: "I don't fully recognise that under David Cameron you have seen Britain in the pocket of the United States, I just don't think that's been the case."
He added: "The UK is becoming more of a niche player and has to be selective as to where it engages and where it doesn't."
Dr Niblett said the UK and the EU always had a difficult relationship, adding that the UK was "already detached somewhat" from the centre of EU decision making.
He said a future Conservative referendum on Eu membership under David Cameron has a "reasonably good chance" of getting a yes vote to stay in the EU. That would enable the country to make gains in other areas it wouldn't be "heavily distracted for two years, almost out of the game" while it focused on the referendum.
If Labour leader Ed Miliband formed the next government then Britain would probably not have a referendum, he said.
Dr Niblett said that given Labour had a "bad history" on giving the British people a vote on treaty change, the "Labour Party would constantly be having to prove that it could be trusted with the British national interest in an EU that is integrated, that somehow the UK under Labour may not fight Britain's corner as toughly as David Cameron would having promised that he was going to do a referendum".
A defeat would "very possibly" prompt the Tory party to elect a more right-leaning and more eurosceptic leader.
Dr Niblett said calling an in-out referendum without something to call it around, and even with something to call it around, was the "wrong call".
He said: "My view is that it is inescapable that at some point, in my time horizon, which is 10 to 15 years, a British government will need to do an in-out referendum, because things will happen such that it will be irresistible."
He added: "I am not confident that Ed Miliband winning puts us in a better position in 2022 or 2023. I am just not happy that Britain has committed to an in-out referendum when, in my opinion, it didn't need to do it.
"I think a British government can play very hard ball with the EU without having to threaten an in-out referendum, it's been done before."