Donald Trump and Joe Biden have won their respective primaries in New Hampshire.

       The former president attacked his last remaining challenger Nikki Haley for staying in the race even as he’s pulling ahead in the delegate count.

       Ms Haley, a former South Carolina governor, said in her speech on Tuesday night that the race is “far from over”.

       “There are dozens of states left to go... and the next one is my sweet state of South Carolina,” she told the crowd in the state capitol of Concord.

       A frustrated Mr Trump appeared to threaten his former UN ambassador, saying that she’ll be under investigation for “stuff she doesn’t want to talk about”.

       With 91 per cent of the vote counted on Wednesday morning, Mr Trump was leading Ms Haley in the Granite State by 54.6 per cent to 43.2 per cent, roughly in line with the 11 percentage point gap estimated by the final opinion polls before the primary.

       Mr Biden did not appear on Democratic ballot papers following a feud with organisers, but a write-in campaign ensured his victory in the symbolic Democratic primary in the state.