Radek Sikorski, a former Polish foreign minister with longstanding ties to Britain, says he is "very worried" British voters could opt to leave the European Union, fearing it could weaken a political arrangement that has given Europe's its longest-ever period of peace and prosperity.

Speaking to The Associated Press on Monday, Sikorski argued that a weaker EU would be particularly risky for nations like his own, which has historically been at the mercy of its large neighbors Russia and Germany.

He said he believes that a British departure from the common bloc would benefit Russia and also leave Germany with greater decision-making weight within the bloc.

Britain is holding a referendum on June 23 to decide whether to leave the EU or remain.