A US federal judge has sentenced former House of Representatives Speaker Dennis Hastert to 15 months in prison for attempted bribery to cover up sexual assaults.

Prosecutors had recommended a shorter term, but the judge felt that the earlier crimes of sexual assault demanded a more severe punishment.

Hastert accepted a plea bargain, during which he acknowledged offering $3.5 million in order to cover up allegations that he had sexually assaulted high school students while working as a wrestling coach.