Ms Hirst, who is the party's deputy chairman, claims she has not been invited to any hustings during the by-election campaign or been given fair coverage in the media, intends to make a formal complaint to the Electoral Commission and Ofcom about the matter.
In a statement she said: “It is outrageous that there seems to be a deliberate attempt to air-brush me out the picture because the opposition parties do not want to let the electorate hear what I have to say and offer.
"The only conclusion I can draw is that they are scared that the people of Batley and Spen might actually vote for a party that will do what they say will and represent their interests in Westminster."
She added: "One would think that there were only two candidates running in this by-election: Kim Leadbeater, the Labour candidate, and George Galloway, from the Worker’s Party.
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"I came second in the 2016 by-election and am one of most experienced candidates standing.
"The people of Batley and Spen deserve to be able to listen to other candidates and decide for themselves on the basis of what they see and hear who to vote for.”