Pope Francis warned heads of states attending the annual G20 meeting in Australia about the effects of “unbridled consumerism” and called on them to take concrete steps to alleviate unemployment.

In a letter addressed to Australia Prime Minister Tony Abbott, who is chairing this year’s G20 Leaders’ Summit which begins Sunday, the Pontiff called for its participants to consider that “many lives are at stake.”

“It would indeed be regrettable if such discussions were to remain purely on the level of declarations of principle,” Pope Francis wrote in the letter.

Pope Francis, who has made a habit of addressing the leaders of the G20 meetings, has often raised his concerns with the global economy. Last year, in lengthy report airing the views of the Vatican, he criticized the “idolatry of money” and denounced the unfettered free market as the “new tyranny.”

In the letter published Tuesday, he said that, like attacks on human rights in the Middle East, abuses in the financial system are among the “forms of aggression that are less evident but equally real and serious.”

“Responsibility for the poor and the marginalized must therefore be an essential element of any political decision, whether on the national or the international level,” he wrote.

Write to Noah Rayman at noah.rayman@time.com.