The French far-right leader Marine Le Pen has suggested the Italian prime minister, Giorgia Meloni, join forces with her in a new alliance, as the EU’s resurgent but divided nationalist parties gear up for European parliamentary elections next month.

The move came as European centre-left parties reiterated a warning to the European Commission president, Ursula von der Leyen, that they would not support her bid for a second term if it entailed the backing of hard-right parties – including Meloni’s.

“Now is the time to unite, it would be really helpful,” Le Pen told the Corriere della Sera newspaper. “If we succeed we can be the second group in the European parliament. I think we shouldn’t miss an opportunity like this.”

Le Pen’s invitation came after her National Rally (RN) said it would no longer sit with Alternative für Deutschland (AfD) in the parliament, and her pan-European far-right group, Identity and Democracy (ID), expelled the German party as too toxic.

That left Europe’s national-conservative and far-right parties – who agree on some issues, such as immigration and the rolling back of green regulations, but are fiercely opposed on others, including support for Ukraine – in disarray.

Le Pen’s offer would imply a wholesale reconfiguration of the hard right in the parliament, since Meloni’s Brothers of Italy party sits in the assembly’s other nationalist group, the European Conservatives and Reformists (ECR).

Although polls predict hard-right parties may return a record 165 MEPs in the 720-seat assembly after the 6-9 June ballot, as things stand they would be scattered between two discordant parliamentary groups and two non-affiliated national delegations.

Le Pen’s radical ID group includes Geert Wilders’s Dutch Freedom party (PVV) and Austria’s Freedom party (FPÖ), while Meloni’s more normalised ECR includes Poland’s Law & Justice party (PiS) and Spain’s Vox.

Meanwhile, 14 MEPs likely to be returned by Viktor Orbán’s Fidesz party, plus up to 17 expected to be won by AfD, would be “non-inscrit”, or without a parliamentary group, depriving them of much of their influence.

Le Pen’s proposed hard-right “super-group” is seen as highly unlikely to materialise given the parties’ factional rivalries, but whether and how they realign could well have an impact on the assembly’s workings and, ultimately, the EU’s functioning.

Analysts say Meloni’s role in the post-election process will be key. The Italian prime minister has so far proved largely constructive within the EU, winning the backing of the centre-right von der Leyen.

That has given Meloni unexpected influence at EU level which, were she to realign herself with the likes of Orbán and Le Pen, she would inevitably lose. Moreover, many ECR members would not countenance cooperation with more Moscow-friendly ID parties.

“Meloni finds herself with two outstretched hands before the elections – one from Le Pen, the other from von der Leyen,” said Nicolai von Ondarza, of the German Institute for International Affairs. “She will be able to take only one.”

Meloni said on Sunday she ruled nothing out. “My principal objective is to build an alternative majority to the one that has governed in recent years, a centre-right majority … that will send the left into opposition,” she told Italian television.

But von der Leyen, who has repeatedly said she would be willing to work with Meloni and the ECR group after the elections, faces a dilemma too.

Both the centrist Renew group and the centre-left Socialists and Democrats (S&D), set to finish second in the ballot behind her centre-right European People’s party (EPP), have warned the outgoing commission chief against any deal with the hard right.

Leading leftwingers last week issued a declaration ruling out alliances with the far right, and S&D group officials have said the group would not back von der Leyen for a second term as commission president if she sought support from far-right parties.

Germany’s centre-left chancellor, Olaf Scholz, said on Friday the next commission “must not be based on a majority that also needs the support of the far right”, and its president could only be chosen based on support from “the traditional parties”.