After competing in the Czech Rally Championship for four years, Prokop debuted in the World Rally Championship at the 2005 Monte Carlo Rally, finishing ninth in the Junior World Rally Championship (JWRC) category. He ended his season with the same position in the overall junior standings. In the 2006 season, Prokop took his first JWRC win at the Rally Catalunya and finished tenth in the championship.[1]
In 2009, Prokop continued competing in both WRC support championships. In August 2009, he secured the junior world title with a win at the Rally Finland, after earlier driving his Citroën C2 S1600 to victory in Cyprus and Italy.[2] He finished 2nd in PWRC 2009 standings after Armindo Araujo.