Spain’s deputy prime minister, the outspoken Socialist Teresa Ribera, will take charge of Europe’s “clean transition” and antitrust enforcement, in a powerful role at the heart of the next European Commission.

Ribera is to become one of six executive vice-presidents in the incoming EU executive led by Ursula von der Leyen, which is expected to start work at the end of the year.

The French president Emmanuel Macron’s close ally Stéphane Séjourné, another vice-president pick, gets a sprawling portfolio in charge of industrial policy, while the Italian far-right leader Giorgia Meloni’s choice, Raffaele Fitto, will oversee funding for Europe’s poorer regions.

Von der Leyen, the first woman to lead the commission, outlined the choices for her team of 26 top officials in Strasbourg on Tuesday. After weeks of wrangling with national capitals that nominate candidates, the final list was a careful balancing act of geography, party affiliation and gender.

It was also a show of strength by von der Leyen, who strong-armed some governments into providing female candidates. She oversaw the departure of some of her sternest critics, including France’s Thierry Breton, who was expected to serve a second-term in Brussels until his shock resignation on Monday, when he criticised “questionable governance” at the commission.

The decision to award Fitto a vice-presidential post is already proving controversial in the European parliament, however, especially among Green and Socialist MEPs whose support was crucial to von der Leyen’s successful reelection in July.

Defending the move, the commission president noted that two of the European parliament’s 14 vice-presidents came from Fitto’s ECR faction. “Italy is a very important country and one of our founding members and this also has to reflect in the choice,” she said. It was perhaps a tacit admission that while all member states are equal under the EU treaties, some carry more weight than others.

The co-leader of the Green group Terry Reintke said Fitto’s nomination to a vice-presidency was “a big concern for our group” and “could endanger the pro-democratic majority in the European parliament that voted for Ursula von der Leyen in July”.

Ribera, a veteran advocate of climate action, has been tasked with leading the EU’s “clean industrial deal” to promote green companies that von der Leyen promised to publish in the first 100 days of her next mandate. Ribera, von der Leyen said, would “make sure Europe remains on track during the European green deal”.

The climate emergency “is the major backdrop of all we are doing”, von der Leyen said, while adding that security and Europe’s competitiveness had also emerged as dominant themes in setting the priorities for her incoming commission. The former Italian prime minister Mario Draghi last week warned that Europe needed an €800bn spending boost plus deep-rooted reforms to avert a “slow and agonising decline”.

Citing the Draghi report, von der Leyen also tasked Ribera with leading the work to bring down European energy prices and end dependency on fossil fuels.

In an unprecedented move, Ribera has also been designated competition commissioner, traditionally one of the most powerful jobs in Brussels. She will be following in the footsteps of Margrethe Vestager, the high-flying Danish politician who ordered Apple to repay €13bn in underpaid taxes during a decade-long crusade against “aggressive tax planning”.

Four of the six vice-president nominees are women, while the overall team of EU commissioners is 40% female. While this falls short of von der Leyen’s aim of achieving a gender-balanced commission, it is an improvement on a few weeks ago, when barely one-fifth of the candidates were women.

Von der Leyen told reporters that she had been on track for 22% women and 78% men, which was “completely unacceptable, so I worked intensively with the member states and we were able to improve the share”.

For the first time there will be EU commissioners for defence (Lithuania’s former prime minister Andrius Kubilius) and housing (Denmark’s Dan Jørgensen, who is also in charge of energy policy). Croatia’s Dubravka Šuica the only woman to return to the commission for a second term, apart from von der Leyen, gets the new job of commissioner for the Mediterranean.

Another returnee, the Netherlands’ Wopke Hoekstra, will be commissioner for climate, net zero and clean growth and is expected to represent the bloc in international negotiations on the climate crisis. On paper, he and Jørgensen are more junior to Ribera.

Luxembourg MEP, Christophe Hansen, has been appointed farming commissioner. A member of the centre-right European People’s party, Hansen and Hoekstra are seen as balancing Ribera, whose appointment to a big climate role has unnerved some centre-right politicians.

Ribera is not afraid to speak her mind. In the run-up to the European elections, she criticised von der Leyen for refusing to rule out working with Meloni’s hard-right European Conservatives and Reformists faction.

The EPP celebrated having 14 of the 27 places at the commission’s top table, including von der Leyen, cementing its dominance as Europe’s strongest political force that has won every European election for 25 years.

EU commissioners are akin to government ministers: they are responsible for drafting and enforcing EU laws on climate and nature protection, the single market, economy technology, energy, as well as overseeing the bloc’s foreign policy and negotiating trade deals.

Each EU member state sends a commissioner to Brussels, who is meant to represent the common European interest, rather than national positions. All commissioner candidates will be questioned in the European parliament in hearings expected to take place in October. MEPs typically reject two or three commissioners, before voting on whether to approve the entire commission.

Hungary’s nominee, Olivér Várhelyi, picked for a second term, is seen as especially vulnerable.

EU officials expect the new commission to take office on 1 December.