Lucke and four other AfD European parliamentarians called a press conference for Tuesday in Strasbourg. Reports on Monday said they had already founded a new association called "Weckruf 2015," or "Wake-up call 2015."

In a message to members, Lucke said he did not believe that appeals for unity helped any more.

"The fundamental attitudes of these two groups are irreconcilable," Lucke wrote in an open letter, a clear allusion to the growing right-wing influences on AfD policies - people more troubled by the EU's rules on migration, for instance, than on the economic merits of monetary union.

"We are not willing to serve as a serious facade in civil society for these groups," Lucke and his allies told party members in their letter.

New party intended?

His rival, Frauke Petry, an AfD co-chairperson who also heads the AfD's eastern Saxony state branch, called on Lucke on Monday to distance himself from the reports that a new association or party was intended.

Lucke, a free-market economics professor vehemently opposed to European monetary union, co-founded the AfD in 2013 to protest German and EU-wide policies during the eurozone debt crisis.

It unsettled German politics by creating an opposition alternative to the right of Germany's conservative Christian Democrats led by Chancellor Angela Merkel.

The AfD fell narrowly short of being elected to the German federal parliament in September 2013, just missing the 5-percent hurdle that guarantees representation.

Footholds in five assemblies

Since then, however, it has gained opposition footholds in the European Parliament and in five German regional parlaiments, the latest being the city-state of Bremen.

A fellow market liberal and former German industry leader, Hans-Olaf Henkel, resigned his party executive seat last month after clashing with what he termed "right-wing ideologues" in the AfD.

Lucke said on Monday that if the AfD failed at its federal party conference on June 13 to isolate itself from the "machinations" of right-wing nationalists then the formation of a new party was possibly the only way forward.

"We don't see a future for us in the AfD if the party doesn't decisively resist those who while brawling try to draw attention to themselves or peddle on the fringe of society," wrote Lucke and his supporters.

Early this month, the German business newspaper "Handelsblatt" reported that the AfD has 21,226 members plus a further 1,502 supporters who donate money.

ipj/xx (dpa, AFP)