Hillary Clinton fears over Kaminski

Pushed as to whether the fears were raised directly with David Miliband, the official added: "just say HC was concerned."

Mrs Clinton’s visit coincided with the latest intervention by Foreign Secretary David Miliband, who wrote in this week’s Observer that the Conservatives were putting relations with the international community at risk. He was responding to an interview in the JC with the Polish leader of the ECR, Michal Kaminski, who suggested that a massacre by Poles of hundreds of Jews at Jedwabne in 1941 should be considered a lesser crime than those of the Nazis.

The news of US diplomatic concerns partly explains Mr Miliband’s comments in the Observer that “there will be incredulity in Washington, Beijing and Delhi, never mind Berlin and Paris”.

The JC understands that Washington’s fears focus on the consequences of the alliance for relations between the United States and the European Union in the event of a Conservative election victory next year. Britain has traditionally acted as the diplomatic bridge between Europe and America.

Controversy over Mr Kaminski’s past grew this week after he was forced to admit wearing a symbol associated with totalitarian Catholic groups.

His party has also been associated with the controversial broadcaster Radio Maryja. The ultra-traditionalist Catholic radio station was sued for defamation by the Union of Jewish Religious Communities of Poland last year following antisemitic remarks by the station’s charismatic head, Father Tadeusz Rydzyk.

The station has been the main cheerleader for Mr Kaminski’s Law and Justice party and was prominent in campaigning during this year’s European elections.

In 2007, in a report for the Council of Europe on combating antisemitism, Radio Maryja was named as a major source of antisemitic propaganda.

The Conservative Party said last night they have received no messages of concern about their new European partners from any foreign government.