Jack Straw has become involved in the controversy surrounding John Bolton, President Bush's choice to become the next American ambassador to the United Nations.

It was reported that Straw told Colin Powell, the former US secretary of state, that Bolton was trying to destroy a European initiative on Iran's nuclear programme.

Straw made the complaint after he became convinced that Bolton was the source of a newspaper article which quoted an unnamed senior US official who dismissed the initiative as "spring training" and advocated "regime change" in Tehran.

A Foreign Office spokesman said last night that Straw had "no recollection" of clashing with the nominee.