The far-right National Rally (RN) has strengthened in final polls, including one suggesting it could be on course for a historic parliamentary majority, as candidates fought for votes on the last day of campaigning before the first-round ballot in France’s most momentous election for decades. Two days before Sunday’s ballot, two polls on Friday showed Marine Le Pen’s anti-immigration, France-first party pulling steadily further ahead in a race it has led since President Emmanuel Macron called the shock ballot almost three weeks ago after the defeat of his centrists in the European parliamentary election. Official campaigning for the first round vote ends at midnight on Friday, with no political activity allowed on Saturday. Campaigning resumes on Monday for a final five days before a decisive second round ballot on 7 July in which the party could take control of France’s government for the first time. One poll, for Les Echos newspaper, showed RN could win 37% of the national vote, two points more than a week ago, while another, for BFM TV, estimated the far-right party was on course for 260-295 seats – potentially giving it an outright majority. RN, which has pledged to boost spending power, slash immigration and restore law and order, “cannot only envisage a relative majority, but we cannot exclude – far from it – an absolute majority” of 289 deputies, Brice Teinturier, the deputy director of a third polling agency, Ipsos, told Agence France-Presse. The New Popular Front (NFP), a broad but fractious leftwing alliance dominated by the Unbowed France (LFI) of the veteran radical left firebrand Jean-Luc Mélenchon, was on 28%, and Macron’s centrist bloc, known as Together, on 20%. Accurate seat forecasts are difficult because the outcome depends on second-round results in France’s 577 constituencies, many of which could be three-way races and affected by tactical alliances and withdrawals aimed at blocking the far right. “Of course I want to avoid the extremes, especially the far right, being able to win,” the prime minister, Gabriel Attal, said on Friday. Macron, who has called both the left and far right extreme, also suggested at an EU summit on Thursday that prospective Together MPs would back moderate left candidates against far-right ones. The president also criticised far-right “arrogance”, saying it had “already allocated all the government jobs” and questioned his constitutional role as military commander-in-chief. “Who are they to explain what the constitution should say?” he asked. A hung parliament, with Macron’s forces squeezed between two hostile bigger blocs, would lead to near-certain deadlock, while an RN majority would deliver a fraught cohabitation with a party radically opposed to the president on almost everything. Le Pen hinted at the kind of rows that could arise on Friday, saying it was “the prime minister’s prerogative, not the president’s” to name France’s next European commissioner – currently the internal markets commissioner, Thierry Breton. RN’s youthful president, 28-year-old Jordan Bardella, has said he will not take up the post of prime minister unless his party, which has toned down some of its anti-EU positions and pledged fiscal responsibility, wins an absolute majority. But the party remains vague about the cost of its promises, which include cutting VAT on all energy and, longer term, abolishing Macron’s pension reform to return the state pension age to between 60 and 62 and exempting all under-30s from income tax. RN also aims to abolish the right of babies born in France to be French, which would almost certainly be declared unconstitutional by France’s constitutional council, and to create a “national preference” for some welfare payments in breach of EU rules. Analysts say the far-right party has benefited from public anger at Macron, whose pro-business reforms have spurred the economy but who is seen by many voters as having ignored their concerns about the cost of living and worsening public services. His popularity has sunk so low allies suggested he take a backseat in the campaign. In a televised debate on Thursday evening, Bardella sought to reassure voters about RN’s foreign policy, saying he would “not let Russian imperialism absorb an allied state like Ukraine”, although he was opposed to sending long-range missiles to Kyiv. The RN president dismissed as “utterly false” reports in French media that as many as 100 RN candidates standing in the election had been found to have made “racist, antisemitic and homophobic comments” in the past. Separately on Thursday, France’s media watchdog, Arcom, warned one of the country’s leading radio stations, Europe 1, over a two-hour elections talkshow presented every morning during the campaign by the controversial host Cyril Hanouna. Hanouna, whose evening TV show has been fined a total of €7.5m (£6.36m) by Arcom for breaching rules on political balance, recently told listeners the leftist NFP alliance sought “the destruction of the republic, of the country and of our civilisation”. The regulator said Hanouna’s show was systematically favouring RN and treating leftwing parties “in a systematically critical and virulent manner, in terms that were often derogatory and outrageous”, reflecting “a lack of measure and honesty”.