The French prime minister, Gabriel Attal, has urged all political parties to call for calm on a tense last day of campaigning for a snap election in which the far right hopes to win a majority in parliament. “Violence and intimidation have no place in our society,” Attal wrote in a social media post. The interior minister, Gérald Darmanin, said: “This campaign is short and yet we already have 51 candidates, substitutes and activists who have been physically assaulted.” Darmanin told BFM TV that some of the assaults had been extremely serious and led to people being admitted to hospital. He said more than 30 arrests had been made across France and denounced what he called “a climate of great violence towards politics and all that it represents”. It was too early to establish a “typical profile” of the people carrying out the attacks, but they ranged from people who had “spontaneously got angry” to “political activists either from the ultra-left or ultra-right”. The assaults had happened against people on all sides, he said. About 30,000 police will be deployed across France after the results on Sunday, including 5,000 in Paris and the surrounding area. Darmanin said he feared “excesses” and had asked the Paris police chief to ban street protests expected outside parliament on Sunday night. He said he feared the “ultra-left” above all. He also said he anticipated demonstrations in Lyon, Rennes and Nantes or “anywhere there is the ultra-right or ultra-left”. The Paris Bar Council has asked the public prosecutor’s office to open a case after a far-right website called for the “elimination” of lawyers who had signed an article against Marine Le Pen’s anti-immigration National Rally (RN). The far-right party has said it could win an absolute majority of 289 seats in parliament and form a government. Latest polling, however, suggests it will fall short of that target, but it is expected to become the largest party. An Ipsos poll forecast the RN would get between 175 and 205 seats and Ifop pollsters put the figure at between 170 and 210. Polls also showed that tactical voting could limit the RN’s gains. Emmanuel Macron’s centrists and a broad leftwing coalition agreed this week to withdraw more than 200 candidates from the final round to avoid splitting the vote against the RN. Polls suggest only between a third and a half of centrists could switch to the leftwing alliance to fend off the far right, while perhaps two-thirds of left-leaning voters could back a centrist. If the RN and its allies do not win an absolute majority but end up as the largest party, there could be deadlock in parliament and a struggle to form a government. Le Pen said on Friday that such deadlock would “not [be] chaos but a quagmire, a total standstill”, urging her supporters to turn out and give her party the biggest score possible. She said that if the RN did not have a clear majority, “no law will be voted ... for a year, the country will be at standstill at the worst moment for France”. If no party reaches a clear majority, there is uncertainty about how a government could be formed, weeks before Paris hosts the Olympics. Attal, an ally of Macron, was campaigning on Friday in Paris and did not rule out his minority administration remaining in place for “as long as necessary” after polling day. That was understood to mean the government could continue for a brief period in case of deadlock in parliament, but Attal did not explain further. The president’s decision to call a snap vote three years ahead of schedule after his party was trounced by the far right in European elections was seen as the biggest gamble of his political career. He said at the time that it would allow French people to reject extremes and reset parliament. Predictions are hard to make before Sunday’s second round but polling showed Macron’s centrists losing ground and the far right gaining support.