Alessandra Mussolini, grand-daughter of Italy's fascist dictator Benito Mussolini, has been barred from taking part in next month's regional polls.
Mussolini (left) and rival Gianfranco Fini were once allies
An appeal court in the Italian capital Rome ruled that almost 1,000 of the signatures supporting her far-right candidacy were fake.
Ms Mussolini blamed her former party, the right-wing National Alliance.
She also announced that she would start a hunger strike on Monday in protest at the decision.
She had intended to run for the influential post of president of Lazio, a region of Rome, standing against the incumbent Francesco Storace, a former party comrade.
Split with party
In 2003, Ms Mussolini left the National Alliance - which has a fascist past - after the party leader, Gianfranco Fini, described fascism as "absolute evil".
Mr Fini, now Italy's foreign minister, has since moved the party into the political mainstream.
Ms Mussolini subsequently on to found the far-right party Liberta d'Azione, with which she won a seat at the European Parliament in last year's elections.
Italy's regional elections are scheduled for 3-4 April.