Germany's Green party on Monday named co-chair Annalena Baerbock as its candidate to succeed Angela Merkel, throwing down the gauntlet to the chancellor's conservatives who are locked in increasingly vicious infighting for her crown.

Trained lawyer Baerbock, 40, became the first chancellor candidate for the party, as surging support for Greens brings it within reach of the chancellery.

Both Baerbock and her fellow co-chair Robert Habeck, 51, had coveted the job to lead the party into elections on September 26.

"But in the end, only one can do it. So today is the moment to say that the Greens' first chancellor candidate will be Annalena Baerbock," said Habeck.

Green party leader Annalena Baerbock has been described as someone "who won't be fobbed off" when drilling into complex issues
Green party leader Annalena Baerbock has been described as someone "who won't be fobbed off" when drilling into complex issues AFP / John MACDOUGALL

With her candidacy, Baerbock said she was making an "offer to the entire society".

"Climate change is the task our of time, the task of my generation. And accordingly, I want the policies of the new federal government to make climate protection the benchmark for all sectors," she pledged.

The carefully choreographed announcement stood in sharp contrast to a bruising power struggle that has sent Merkel's CDU-CSU alliance to the brink of implosion.

Green party leader Robert Habeck walked into a local politics gathering in 2002 to seek cycling lanes, and 10 years later was the environment minister for Schleswig-Holstein state
Green party leader Robert Habeck walked into a local politics gathering in 2002 to seek cycling lanes, and 10 years later was the environment minister for Schleswig-Holstein state AFP / John MACDOUGALL

Ahead of Monday's announcement, the Greens had shown strict discipline in preventing any internal wrangling from spilling out into the public.

Surveys show the centre-left party just a touch behind Merkel's conservatives -- who are in disarray as the veteran chancellor prepares to bow out after 16 years in power.

Baerbock voiced "great concern" that the ruling conservatives are "faltering" at a time of "great challenges".

Besides a damaging power struggle, Merkel's alliance is also suffering in the polls over the public's frustration over the handling of the coronavirus pandemic.

In contrast, the ecologist party has quietly benefited from a firm line seeking tougher measures to curb coronavirus transmission.

Merkel is stepping down after 16 years in power
Merkel is stepping down after 16 years in power POOL / Michael Sohn

The Greens' environmentalist platform also dovetails with the priorities of many younger Germans, who rattled the political establishment with school strikes for climate protection until the pandemic put such gatherings on ice.

The decision to name a chancellor candidate is a clear sign that the party which played a junior role in Gerhard Schroeder's coalition from 1998 to 2005 are now no longer content with settling for a kingmaker role.

On a regional level, the Greens are now part of government coalitions in more than half of Germany's 16 states, including in Baden-Wuerttemberg, homeground of auto giant Daimler.

Merkel led congratulations from German political leaders to Baerbock for the nomination.

With a reputation as someone who knows her brief inside out and with strong ties to the grassroots, Baerbock has stepped out of the shadows to run neck-and-neck with Habeck in popularity rankings.

In November 2019, an opinion poll found just 11 percent believed she would be a good chancellor candidate, as compared to 42 percent for Habeck.

Observers have described her as someone "who won't be fobbed off" when drilling into complex issues, in an echo of Merkel's methodical and science-based approach to policy.

A former trampolining ace who studied public international law at the London School of Economics, Baerbock has never held a government role.

Critics have honed in on her lack of government experience, raising doubts about her preparation for the election battle and the likely coalition haggling afterwards.

But the sharp-witted former journalist and a mother of two has countered that "three years as party leader, being a lawmaker and mother of young children tend to toughen you up".

On Monday, she also directly batted off critics.

"Yes I've never been chancellor, or minister. I stand for renewal," she said.

"Others stand for the status quo. I'm convinced that this country needs a new beginning to meet the new challenges of the coming decades."