The US President made the slip while honouring Jan Karski, a Polish resistance fighter who was among the first to raise the alarm over the Nazi concentration camps, during a ceremony at the White House.

Poland has long been sensitive to any implication that it was involved in the Holocaust, accurately pointing out that the camps on Polish soil were run by occupying German forces.

Foreign Minister Radek Sikorsi took to Twitter to insist that the White House apologise for the “outrageous error” and said that Prime Minister Donald Tusk would make a statement on Wednesday morning.

“It’s a pity that this important ceremony was upstaged by ignorance and incompetence,” he wrote.

Mr Obama’s gaffe was widely reported on Polish television and on Twitter.

Tommy Vietor, the President’s National Security Council Spokesman, issued a clarifying statement but stopped short of an apology.

“The President was referring to Nazi death camps operated in Poland. The President has demonstrated in word and deed his rock-solid commitment to our close alliance with Poland,” he said, according to the Economist.

Such is Poland’s sensitivity on the subject, its embassy in Washington carries an extensive online fact sheet advising on how to correct journalists who use the phrase “Polish death camp”.

“We cannot allow history to be distorted,” the guide says.

While Poland remains a staunch US ally – and has 2,500 troops in Afghanistan, making it the sixth-largest contributor – relations between its government and the Obama administration have sometimes been strained.

Some in Poland felt betrayed by Mr Obama’s decision to abandon George W Bush’s plans for a European missile defence shield, which would have been based in Poland and the Czech Republic.

The proposals had been furiously opposed by Russia.