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German Chancellor Angela Merkel fired her environment minister on Wednesday after he led her conservative party to an embarrassingly heavy state election defeat.

Merkel said she had asked Germany's president to dismiss Norbert Roettgen and replace him with Peter Altmaier, a trusted senior lawmaker who has been her party's chief whip since 2009 and helped organize parliamentary majorities for her eurozone rescue plans.

She said in a brief statement to reporters that a "new beginning" was needed at the Environment Ministry as Germany works to phase out nuclear power and transition to renewable energy sources, and left without taking questions.

Merkel dumped Roettgen after her Christian Democratic Union -- with the minister as its candidate for governor -- slumped Sunday to its worst state election showing since World War II in North Rhine-Westphalia, Germany's most populous state.

Roettgen's challenge to the state's popular center-left governor, Hannelore Kraft, was marred by a series of gaffes that this week drew open criticism from fellow conservatives. He already had quit as head of the Christian Democrats' local branch.

Roettgen never looked seriously likely to win back North Rhine-Westphalia, a state that Merkel's party lost two years ago, in Sunday's election. But the scale of his defeat -- the party dropped from 34.6 percent of the vote to just 26.3 percent -- was a surprise.

During the campaign, Roettgen faced criticism for not committing himself to stay in state-level politics whether he won or lost. In a lengthy rant on public television Monday, Horst Seehofer, a senior conservative ally of Merkel, said that was "a very big mistake" and cost him credibility.

In the closing days of the campaign, Roettgen -- an ambitious figure who was widely believed to have designs on a future run for the chancellery -- raised eyebrows by saying, in an apparent attempt at irony, that "regrettably" voters rather than his party would decide whether he became governor.

Merkel's party labeled Kraft's state government as irresponsibly spendthrift but was then criticized for failing to offer detailed plans for cuts.

Roettgen also irritated the chancellor by declaring Sunday's election would decide "whether Angela Merkel's course in Europe is strengthened or whether it is weakened by the re-election of a pro-debt government in Germany." Following the comment, Merkel emphasized it was an important state election, "no more and no less."

The disastrous election result and subsequent sniping raised questions as to whether Roettgen could credibly continue overseeing one of the government's biggest projects: Germany's transition to renewable energy sources as it phases out nuclear power.

Merkel said in Wednesday's announcement that that is "one of the central projects of this parliamentary term," which ends next year. "The foundations have been laid, but we still have plenty of work in front of us."

The job now goes to Altmaier, a former deputy interior minister who has become an increasingly prominent figure in the chancellor's party over the past two years.