The former French prime minister Manuel Valls has formally announced his candidacy for mayor of Barcelona, joining a rare club of politicians who have run for office in two countries.

Valls said he wanted to lead a coalition focused on “poverty, unemployment, racism and social injustice” rather than the vexed issue of Catalan independence.

Speaking in Catalan, Spanish and French to a packed meeting in Barcelona on Tuesday evening, the former socialist, who has since shifted to the right, said: “Barcelona deserves to be governed thinking about the city and not other projects that have nothing to do with the city itself.”

He said Barcelona should be “an antidote against populism” and “a meeting point and a space of co-existence”.

Valls, 56, said he would resign as a French MP to clear the way for his run. He has not revealed who else might join his coalition, but said the platform would be called Barcelona, European Capital.

Despite Valls’ words, the mayoral campaign is likely to serve as a proxy battle in the wider independence war. His main rival will be the incumbent, Ada Colau, who has tried to remain above the independence fray and has been criticised over crime levels and the proliferation of street vendors.

The centre-right Citizens party – which has been a vociferous opponent of Catalan independence, and which was the single biggest winner in last December’s regional election – gave Valls’ candidacy an enthusiastic welcome.

“There is no one better to recover Barcelona’s prestige and defeat separatism and populism at the ballot box,” tweeted its leader, Albert Rivera. “The is great news for our city, for Spain and for all of Europe.”

Barcelona remains the secessionists’ weakest link and a failure to win it would undermine their claim to represent the majority of Catalans. More than half the city’s inhabitants were either born outside Catalonia and retain strong links with the rest of Spain or are immigrants from other countries.

In last year’s snap election, the combined vote for pro-independence parties in the city was 45.7%, while the Citizens party took the most seats. “Secessionism has tried to project the city as the capital of an imaginary republic, but that’s not what Barcelona is,” Valls said.

Valls, who was born in Barcelona while his parents were on holiday but has never lived there, was at pains to assert his close ties to the city, with numerous references to his Catalan father, the artist Xavier Valls, and childhood holidays spent in the city.

In a dig at Colau, Valls vowed to clean up the city, which he claimed had descended into lawlessness.

Colau, whose Barcelona en Comú platform claimed a surprise victory in 2015, will be standing for re-election. For most of the past four years she has had the highest approval ratings of any mayor in the city’s history, but she has few friends in the media or among the secessionists and faces a tough campaign.

However, Valls’ tenuous connection to the city will make him an easy target for Colau, who has deep roots in Barcelona’s tradition of militant, communitarian politics.

“We know we’ve upset the interests of various financial elites and we know these people weren’t going to sit on their hands and were looking for a new candidate,” she said on Wednesday.

Colau said the financial elites had “joined forced with the Citizens party and found a candidate in France”, adding: “I will be delighted to discuss the future of the city with Mr Valls.”

Valls will also probably be up against Ernest Maragall, the likely mayoral candidate for the pro-independence Republican Left, whose leader, Oriol Junqueras, is among the Catalan leaders awaiting trial for their part in last October’s illegal declaration of independence.

Valls’ speech on Tuesday suggested he was aware of the need to concentrate on local issues rather than basing his run on anti-independence sentiments.

Maragall, whose brother Pasqual was Barcelona mayor from 1982 to 1997 and oversaw the successful 1992 Olympic bid, has warned Valls against campaigning on an anti-independence platform, saying the people of the city would not tolerate being used as part of a national issue.

“I would be ill at ease if the only campaign debate was about whether or not Barcelona contributes to the independence of Catalonia,” he told reporters in Madrid on Monday. “Barcelona is the real debate.”

Maragall, who is the Catalan government’s foreign minister, also professed surprise that someone who had never lived in the city should be a candidate.

“But that’s fine,” he said. “We’ll see how he gets on when it comes to Barcelona’s society, culture and institutions. At the moment he seems tied to interests and funding that have nothing to do with Barcelona. Mr Valls seems to want to buy Barcelona in that classic, horrible political strategy you see in rightwingers around the world.”

Nevertheless, Valls could yet prove an attractive alternative for the many conservative Catalans who feel they have been dragged out of their depth as secessionists have wrested the leadership of their party from its traditionally moderate, if nationalist leaders.

Politicians who have served in two countries

The former Sinn Féin leader Gerry Adams won Belfast West in 1983 but refused to take up his seat in Westminster. He served as the constituency’s MP from 1997 to 2011, when he resigned to contest the Louth constituency in that year’s Irish general election. He won and has sat in the Dáil for the past seven years.

After serving as president of Georgia for nine years, Mikheil Saakashvili was appointed governor of Odessa by the Ukrainian president, Petro Poroshenko, in May 2015. He was in post for 18 months before quitting and launching a scathing attack on Poroshenko. The president responded by stripping Saakashvili of his Ukrainian citizenship while the Georgian-born politician was in the US.

Going back a little further, the Greek diplomat Count Ioannis Kapodistrias served as imperial Russia’s foreign minister before becoming the first governor of his homeland in 1828 after its independence from the Ottoman empire.