Maria Corina Machado, who is a former congresswoman, said she was given 15 days to appeal against the decision.
It was not clear on what grounds she was barred but the move could prevent her from standing again for congress in December’s parliamentary election.
Maria Corina Machado led a major street protest against the government in early 2014.
Government opponents have accused President Nicolas Maduro of bullying the opposition ahead of the elections.
Another leading opposition figure, Daniel Ceballos, a former mayor who is also running for parliament, was also banned from holding public office.
Venezuelan media said Daniel Ceballos was disqualified for not presenting a sworn wealth declaration.
Maria Corina Machado was stripped of her seat in the National Assembly last year after accepting an invitation from Panama to speak before the Organization of American States (OAS) to give her account of the wave of unrest which spread through Venezuela in early 2014.
The state prosecutor’s office then charged Maria Corina Machado of taking part in an alleged plot to kill President Nicolas Maduro.
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