There has been speculation that Obama’s foreign policy approach – and his personal history of his grandfather being tortured by British colonial authorities during the Mau Mau rebellion in Kenya – might lead to a cooler relationship than was the case when his predecessor George Bush and Tony Blair went to war together in Iraq and Afghanistan.

Louis Susman insisted that Obama regards the UK as “our most important ally and our best friend” and dismissed the recent row over the liberation of the Lockerbie bomber Abdelbaset al-Megrahi as “a little spat” of the kind that occurs in any happy marriage.

Susman said Washington had not ruled out following Britain in imposing taxes on bankers’ salaries, after the announcement by the chancellor Alistair Darling of a one-off 50% levy which some commentators suggested would drive high-fliers to relocate from London to alternative financial centres such as New York.

In an interview with BBC Radio 4′s The World At One Susman dismissed any suggestion of a cooling in relations since Obama took office a year ago. “I think the special relationship, as we normally define it, is stronger than ever,” he said.

“With the previous relationship, Mr Blair and Mr Bush had not only a governmental relationship but a very personal relationship – it was more like thinking with the same mind all the time – and I think we are going through some of that now, watching the British inquiry into the lead-up to Iraq.

“President Obama considers the UK our most important ally and our best friend. He constantly expresses … our appreciation for the sacrifice which you are making right now in Afghanistan and the bravery and courage of your soldiers who are dying alongside our soldiers.

“When you look at it in terms of intelligence, we share so much of our intelligence with each other to do counter-terrorism. If you look at it militarily, we are moving forward potentially on joint procurement, joint exercises, joint efforts in Iraq and Afghanistan.

“When you look at it in terms of economics and how we are trying in the financial institutions and what we did through the G20 in global co-ordination to stop this terrible recession, I think it is very, very strong.”

Asked about US anger over the decision to allow Megrahi to return to Libya because of his terminal cancer, Susman said: “The special relationship is very strong. It is like a strong marriage. Every once in a while you have a little spat.

“This was a spat. This was a case where friends can disagree.”

He laughed off calls from some US figures for a boycott of Scottish products, saying he still drank Scotch whisky, visited Scottish golf courses and wore Scottish sweaters.

Susman also rejected claims that Obama had failed to consult Nato allies over his decision to increase US troop numbers in Afghanistan by 30,000, saying there was “immense consultation” with Britain, France and other alliance members.

He said environmentalists were wrong to accuse Obama of preventing an ambitious climate change deal at last month’s Copenhagen summit by failing to come forward with an improved offer for US greenhouse gas emission cuts or put a figure on how much America was prepared to contribute to a $100bn (£62bn) global fund to help poorer countries adapt.

Both these issues were matters for congress to approve and it would have been inappropriate for the president to commit himself without first securing its backing, he said.

However, he said: “Every participant in that conference knew when America says we will pay our share of the $100bn, we will pay our share.”

Susman said Gordon Brown had been “a leader” alongside Obama and others in guiding the world out of recession. And he appeared to hold out the possibility that Obama may consider a tax on bankers’ bonuses to match Darling’s 50% levy on those over £25,000.

“In terms of the tax on bonuses, I think we are looking at everything and we are going to have to see how the financial community conducts itself,” he said.

“I’m not sure what we might do. I would only suggest that the G20 talked about deferred compensation and clawbacks and they expect people to act reasonably. We are waiting to see if people act reasonably. We have to keep our options open.”