Germany’s Greens lurched to the left at a party congress in Berlin over the weekend by endorsing a “soak-the-rich” campaign for new taxes, a risky attempt to win power in September’s election that upset the party’s pragmatist wing.

Ignoring warnings against raising too many taxes at once from their most successful leader, Greens state premier Winfried Kretschmann, the 800 delegates voted to push to raise the top income tax rate to 49 per cent from 42 per cent and introduce an annual 1.5 per cent wealth tax on assets above one million euros.

Greens delegates even booed one of their most respected leaders, Tuebingen mayor Boris Palmer, when he said the tax increases were not balanced – a humiliating slap in the face for the “realo” or pragmatic wing that has long ruled the roost.

The Greens’ shift at the congress that ended yesterday seemed calculated to woo left-leaning voters and raise the party’s chances of returning to power after September’s election to end its eight-year stretch in opposition.

The Greens are the world’s most successful pro-environment party after ruling Germany with the Social Democrats (SPD) from 1998 to 2005, but now they are itching to get back into power.