An advert promoting tourism in the US state of New Jersey is at the heart of a federal investigation into the alleged misuse of relief funds.

Governor Chris Christie is being accused of using Hurricane Sandy money for the advert in which he and his family appear.

It is the second federal probe facing the Republican lawmaker within a week.

Although credited for his handling of the aftermath of the devastating storm, Christie is now being investigated for allegations that he chose a production company which bid over $2m more than a rival to make the ad just because of his family’s involvement.

The investigation has prompted an online petition calling on Christie to quit. The scandal could blight his prospects as an early contender for the Republican nomination for the 2016 presidential election.

Christie is already facing questions into claims that his office closed a traffic bridge last week as a political punishment to a local mayor who had refused to back his re-election as gove