BERLIN (Reuters) - A fierce internal critic of German Chancellor Angela Merkel announced on Sunday she would resign from the center-right Christian Democratic Union (CDU) party, accusing Merkel of having harmed the country with her migration policy.

Erika Steinbach’s move could weaken Merkel’s standing among conservative voters ahead of a September election in which the anti-immigrant Alternative for Germany (AfD) party is expected to enter the federal parliament for the first time.

Steinbach strongly criticized Merkel for allowing more than a million refugees into Germany in the past two years, accusing the chancellor of violating the law and not consulting other European Union members before her decision in 2015.

“All this contradicted our current legal situation and also isolated Germany in Europe because of the uncoordinated action,” Steinbach said.

The conservative lawmaker also linked her resignation to Merkel’s decision to accelerate Germany’s shift away from nuclear power and fossil fuels towards renewable sources of energy after the Fukushima disaster in Japan in 2011.

The decision to shut down the country’s oldest nuclear plants and bid farewell to nuclear power as a technology was “without any legal basis”, she said, adding there had been no threat that a similar disaster could happen in Germany.

Steinbach also cited Germany’s participation in euro zone bailout programs for highly indebted countries such as Greece, a policy she said had “unhinged” the EU’s Growth and Stability Pact and violated joint rules.

The 73-year-old politician, a CDU member for more than 40 years, concluded: “That’s not my party anymore.”

Steinbach has become a hate figure in Poland and the Czech Republic for her former role as president of the Association of Expellees - a job in which she documented the fate of Germans expelled from Eastern Europe after World War II.

Steinbach said she would not join another party, but added she hoped the AfD would enter parliament in the next election. “So that there is a real opposition again,” she said.

The AfD’s “flesh is also from the flesh of the CDU,” she said, and had some smart people among its members, but also political extremists.

The AfD was founded in 2013 as an anti-bailout party, but it has broadened its appeal as it was able to benefit from uncertainty and anxiety linked to Merkel’s refugee policy.

The AfD now has seats in 11 of Germany’s 16 federal state assemblies and polls predict it will enter the federal parliament to become the third-strongest party.

An Emnid survey published on Sunday showed support for Merkel’s CDU party down 1 percentage point to 37 percent, while the co-governing center-left Social Democrats (SPD) stood at 21 percent. The AfD was on 12 percent.