An Italian antifascist activist held in prison in Hungary has accepted a candidacy in the European elections that could see her granted immunity and released from jail.

Ilaria Salis, 39, a teacher from Monza, near Milan, was arrested in Budapest in February 2023 after a counter-demonstration against a neo-Nazi rally. She was charged with three counts of attempted assault and accused of being part of an extreme leftwing organisation.

Her case sparked diplomatic protests and anger in Italy after she was brought to court in Hungary in chains, her hands cuffed and feet locked together. She denies the charges, which carry a sentence of up to 24 years in prison.

In a letter to her lawyer, she detailed the conditions she had faced since her arrest: cells infested with rats and bugs, not being allowed to wash for days at a time, and a lack of urgent medical care.

The Italian government has described her treatment by the Hungarian authorities as “humiliating”. The foreign minister, Antonio Tajani, who had summoned the Hungarian ambassador in protest, said: “This time it seems to me [Hungary] has gone too far.” He added that “treating a prisoner in that way really seems inappropriate, not in tune with our legal culture”.

Salis’s nomination to stand for a seat in the European parliament in the June vote was confirmed in statements released by Nicola Fratoianni and Angelo Bonelli of the Greens and Left Alliance. According to Italian media reports, Salis also received offers from the centre-left Italian Democratic party.

The Greens and Left Alliance statement said her candidacy “aims to protect the rights and dignity of a European citizen [and] also from the inertia of the Italian authorities to obtain a rapid release from prison in in favour of house arrest”.

The impact of candidacy on her case is unclear. Precedent suggests Salis will have to await the outcome of the elections, though her lawyer, Gyorgy Magyar, said immunity was granted in Hungary upon the submission of candidate lists.

Hungary could subsequently ask the European parliament to take action. The parliament in 2021 voted to waive the immunity of three MEPs – Carles Puigdemont, Toni Comín and Clara Ponsatí – who had fled Spain after an illegal referendum on Catalan independence. The move was upheld by the European court of justice.

Salis’s father, Roberto Salis, said he feared for his daughter’s safety and emphasised the urgency of bringing her back to Italy as soon as possible.

A year after Salis’s arrest a mural was painted on a wall imagining her death by hanging, as a far-right march commemorating Nazi forces in the second world war passed through Budapest.

“We already know that on Telegram channels, far-right militants were saying they wanted to put Ilaria in a wheelchair,” Roberto Salis said. “[It] is too dangerous for our daughter. We will continue to demand that Ilaria be allowed to serve her sentence in Italy.”

Hungary has defended its treatment of Salis. “Sure, she was restrained in the courtroom, and yes, she had already spent 11 months in detention,” Hungary’s government spokesperson, Zoltán Kovács, wrote on X in January. “But ‘inhumane’? Not really, no. Taken seriously due to the severity of the crime she’s charged with, more likely.”