By Erik Kirschbaum
BERLIN (Reuters) - Germany's Greens, itching to get back into power after eight years in opposition, are embroiled in a row over plans to raise taxes on high earners that looks set to spoil a party congress starting on Friday.
Consistently polling about 15 percent, the Greens hope to form a centre-left coalition with the Social Democrats (SPD) after the September 22 election, but are lagging Chancellor Angela Merkel's centre-right coalition - also likely to fall short of a majority. The SPD-Greens bloc already controls Germany's upper house of parliament, the Bundesrat.
Greens leaders, notorious for quarrelling at election-year congresses, want to raise the top income tax rate to 49 percent from 42 percent and introduce a 15 percent wealth tax on assets over a million euros (852.3 thousand pounds).
Rather than basking in the media spotlight at the weekend as a unified party to show Germans they are ready to rule again, the Greens infighting could turn the congress into a battle that costs votes in September's election.
The Greens state premier of Baden-Wuerttemberg, Winfried Kretschmann, warned party leaders in Berlin against twisting the screws too tightly after the German Chambers of Industry warned Greens tax plans, which include new levy on corporate assets, could endanger 450,000 jobs.
The four Greens leaders, including lead candidates for chancellor Juergen Trittin and Katrin Goering-Eckart, appealed to Kretschmann to dispel fears about the burdens of the party's tax plan that they say would affect only 10 percent of firms.
Careful not to attack Kretschmann, the party's star after he was elected as the first Greens state premier in German history, the leaders nevertheless urged him to back off.
"We'd be delighted if you could help us to reject the false impression you've raised," they wrote in an open letter to Kretschmann, who runs one of Germany's richest states.
POACHING SUPPORT
The world's most successful pro-environment party after seven years in power with the SPD from 1998 to 2005, the Greens started in 1980 as a fringe left-wing movement born in the heat of 1970s radicalism. They have since moved towards the centre.
The Greens have won supporters in rural parts of Germany, increasingly poaching voters away from Merkel's conservatives having also cut into SPD support for years.
The Greens were flying high before the 1998 federal election until a row broke out over petrol tax increases at a party rally in Magdeburg that sent support plunging to six percent from 10 percent. They want to prevent another such debacle.
However, the Greens are expected to debate long into the evening on Friday and Saturday over 2,600 modifications demanded by members to the party manifesto. Party leaders admit the number sounds intimidating but say many of the changes are over grammatical issues or clarity.
"We've got a lot of school teachers in our party," said one Greens leader. "The number shows we're a lively party."
(Additional reporting by Hans-Edzard Busemann; Editing by Louise Ireland)
