Kristalina Georgieva | Illustration by Aiste Stancikaite for POLITICO Kristalina Georgieva to quit Commission for World Bank job A source said the Bulgarian was frustrated with the ‘poisonous’ influence of Jean-Claude Juncker’s chief of staff.

Kristalina Georgieva resigned Friday as vice president of the European Commission to take a job as CEO of the World Bank, after becoming frustrated by the workings at the highest level of the Commission, and fresh off a failed bid to lead the United Nations.

Commission sources said the Bulgarian commissioner, who has been in charge of the budget and administrative portfolio since 2014, has offered to remain in her Brussels post through to the end of December, before starting her newly created position in Washington on January 2, 2017.

Günther Oettinger, the European commissioner from Germany who currently holds the digital portfolio, will take over Georgieva's responsibilities, according to a statement from the Commission.

“The work of the European Commission must go on,” Commission President Jean-Claude Juncker said Friday in a written statement, adding that he accepted Georgieva’s resignation “with great regret.”

“Kristalina Georgieva is an experienced politician for whom I have great respect and I want to thank her for her loyal and committed work as vice president of the European Commission,” Juncker said.

A further reshuffling of Commission portfolios may follow in coming days, adding additional pressure on an EU institution already beset by crises ranging from migration to Brexit to the economy.

While not the first member of the Juncker Commission to resign — Jonathan Hill quit his post in the wake of the U.K.'s vote to leave the EU — Georgieva's departure is the first to be tied to a grievance with how the Commission operates.

Georgieva, effectively the Commission's chief operating officer, has grown increasingly frustrated with how the institution has handled such challenges as migration, Brexit and senior appointments, according to a Commission source close to her. In particular, the source said, Georgieva objects to the working methods of Martin Selmayr, Juncker's chief of staff, and what she perceives a failure to adequately consult on important decisions.

The source said Georgieva considers Selmayr to be a "poisonous" influence on the Commission, and that she had already reached the limits of her patience before the United Nations vote occurred.

One European commissioner POLITICO spoke to said that while Georgieva did not openly express criticism of Juncker or Selmayr, “from her body language” it was clear that frustrations existed.

Georgieva’s frustrations with Selmayr date back to spring 2015 when, according to a senior Commission source, she accused him of interfering in her efforts to shepherd the €315 billion Juncker Investment Plan through the European Parliament and Council, and took a heavy-handed role in the appointment of senior Commission officials.

In a Twitter exchange on Friday afternoon, Georgieva responded to a congratulatory message from Selmayr by calling him "a great partner to work with over the last two years."

Faced with the prospect of another three years working for Juncker and Selmayr after her failed U.N. bid, Georgieva decided to complete her work on the Commission's mid-term budget review and leave, the source said.

Georgieva has long previous experience at the World Bank, where she rose to the rank of vice president during a 17-year stint before her Commission job.

"Global development is her absolute passion," said a Commission source. "She thought long and hard about this decision. In the end she decided to go back to her passion. She joined the Commission in 2010 when her country needed her, but global development is her abiding passion," the source said, dismissing the idea that the move was motivated by frustration with the Commission's leadership.

“Kristalina is a globally recognized leader with a proven track record in improving the lives of those most in need,” said World Bank Group President Jim Yong Kim in a written statement. A World Bank source described Kim as ecstatic about landing Georgieva for the role.

Georgieva's job title will be chief executive officer of the International Bank for Reconstruction and Development and the International Development Association, entities that focus on lending to middle-income and poor countries. She will be based in Washington, and report directly to Kim.

Oettinger is "one of the few commissioners with an interest in budget talks at the College (of Commissioners)," said a Commission source.

In her current Commission role, Georgieva manages a €161 billion annual budget and more than 30,000 staff.

Oettinger, who managed the budget dossier earlier in October while Georgieva campaigned for the U.N. post, would be the first Western European to hold the post since 2004. It is expected that Oettinger will also gain the title of vice president.

Oettinger is "one of the few commissioners with an interest in budget talks at the College (of Commissioners)," said a Commission source.

Whatever the title, Oettinger's new job implies a significant change from a single-policy-focused responsibility towards a broader portfolio that would allow him to get involved in and speak publicly on many issues.

"Oettinger looks into his files before he speaks about an issue. That is what the president appreciates," a Commission source said in September, when Oettinger temporarily took over Georgieva's beat while she campaigned to become U.N. secretary-general. "He spoke competently about the EU budget during an orientation debate in College [of Commissioners]", the source said.

Florian Eder contributed to this article.