Italy’s anti-establishment Five Star Movement (M5S) and far-right the League have asked for more time to form a government as they iron out policy differences.

Matteo Salvini, the leader of the League, and his M5S counterpart, Luigi Di Maio, had been expected to present their programme to Italy’s president, Sergio Mattarella, and name a prime minister on Monday.

Di Maio, 31, was the first to speak to Mattarella, and emerged from the meeting saying “a few more days” were needed to finalise a government contract that included a policy to scrap an increased retirement age and others that would tackle corruption and jail tax evaders.

“We agree that we have to move quickly but as we are writing a programme for the next five years, it’s very important that we do it as well as possible, so we asked for a few more days,” he said.

Comments from Salvini showed that the parties, which between them won more than 50% of the vote in the inconclusive elections in March, still needed to reach a compromise on various issues, namely immigration. The 45-year-old said he wanted his party to have a free rein at cracking down on “the business” of illegal immigration. He said the new administration would only begin “if it can do things”.

Salvini added: “If I go into government I want to do what I promised to do. The last thing I want is to take the president and Italians for a ride.”

Both he and Di Maio are keeping quiet about their choice of prime minister, indicating a struggle to agree on who could lead their coalition government. Di Maio earlier said the candidate would be “a politician and not a technician”.

The pair have been locked in negotiations since Wednesday night. In line with their campaign pledges, they have reportedly reached agreement on introducing a flat tax as low as 15% and a universal basic income. They have also pledged to attempt to renegotiate European treaties.

It is up to Mattarella to grant more time as well as endorse a prime minister, programme and government lineup. If the talks fail, then new elections are likely. Pointing to the rising support for the League in opinion polls, Salvini said that fresh elections would be in the party’s interests but that he would do everything to give Italians a government.