The liberal group in the European Parliament has rejected a request from Italy's populist 5-Star Movement to join its alliance, ending a short-lived courtship.

Alliance of Liberals and Democrats for Europe leader Guy Verhofstadt said late Monday that "there is insufficient common ground to proceed with the request of the 5-Star Movement to join."

In online balloting that ended Monday, 78.5 percent of 5-Star voters agreed to join ALDE, but were rebuffed within hours after the alliance's legislators started discussing the issue. Too many didn't want to be associated with the Italian populist party. Verhofstadt says "there remain fundamental differences on key European issues."

The 5-Star Movement request had briefly sent shockwaves through the European Union legislature. If approved, it would have made the ALDE group the third-largest in the European Parliament behind the EPP Christian Democrats and the S&D socialists. But there was too much internal revolt and too little faith that the Italian movement would retreat from its Euroskeptic stance almost overnight.

"I have come to the conclusion that there are not enough guarantees to push forward a common agenda to reform Europe," said Verhofstadt, who could have used the movement's support in the election for European Parliament president next week.

In a statement, the 5-Star Movement brushed off ALDE's rejection and hinted that it never expected to be accepted anyway. "The delegation of the 5-Star Movement in the European Parliament will continue its work to create an autonomous political group for the next European legislature: the DDM [Direct Democracy Movement]."

It blamed "the establishment" for ganging up against it because it had "made the system quake like it never has before."

The 5-Star Movement previously was part of the European Parliament's EFDD group, where it had Britain's far-right U.K. Independence Party as an ally. When the movement left that group, UKIP's Nigel Farage said 5-Star founder Beppe Grillo "will now join the Euro-fanatic establishment."

In a blog post encouraging supporters to vote for ALDE, Grillo said the decision to leave the EFDD was logical after Britain's vote to leave the EU, since Farage had achieved his aim and the EFDD would lose its reason to exist.

He said that by joining ALDE, the 5-Star Movement would keep its autonomy, but have a greater voice in Strasbourg. "Dear Nigel, our paths have taken a different route," Grillo wrote to Farage, making clear the movement would not return to the EFDD.

Grillo said ALDE and the 5-Star Movement shared similar objectives, including direct democracy, transparency, voting autonomy, simplification of European bureaucracy, resolution of the migration crisis and promotion of a green economy.

Despite the common ground, the ALDE liberals doubted the movement's commitment to stick close enough to its parliamentary line. Verhofstadt said that "on issues of shared interest, such as the environment, transparency and direct democracy," the two would continue to cooperate.