Mr Vanhecke was elected to the European Parliament and is also honorary president of Vlaams Belang.
The former Vlaams Belang leader had threatened to leave the party if dissidents united in the Belfort Group were not reinstated. This did not happen and so Mr Vanhecke quit.
Another prominent Vlaams Belang politician, the party's floor leader in the Senate, Jürgen Ceder, left the party on Tuesday. Mr Ceder opposes the hard line followed by the present party leadership.