France holds parliamentary elections on June 11 and 18.
"If the new Assembly is hostile to us, we would change the electoral law via a referendum organized as soon as next summer, then the president would dissolve the National Assembly," Gilles Lebreton, the FN official told Le Canard Enchaine newspaper.
Le Pen's official manifesto states that she would implement proportional representation with a 30-percent bonus for the party which came first in the election.
France's existing two-round voting system has so far ensured that despite winning about a quarter of the votes in recent elections, the FN has only two members of parliament.
In the 2014 European parliamentary election, the FN came first in France with 24.84 percent of the vote.
Opinion polls show Macron defeating Le Pen on Sunday 60-40.
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