image copyrightAFP/Getty Images

A prominent ally of Donald Trump has urged him to drop his efforts to overturn his loss to Joe Biden in the US presidential election.

Former New Jersey Governor Chris Christie called the president’s legal team a “national embarrassment”.

President Trump has refused to concede the election, making unsubstantiated claims of widespread electoral fraud.

Many Republicans have supported his legal efforts but a small but growing number have broken ranks.

On Saturday Mr Trump suffered a major blow in Pennsylvania, after a judge dismissed a lawsuit from the Trump campaign seeking to invalidate millions of mail-in votes in the battleground state.