Facebook has publicly admitted hiring a public relations firm to find and disseminate information on George Soros, saying that it “wanted to determine if he had any financial motivation” for having criticised the company in a speech.

The social media giant was one of a number of companies to use the services of Definers, a public affairs company specialising in opposition research.

Facebook fired the PR firm last week after the New York Times detailed the actions it had taken after Mr Soros attacked Facebook as a “menace” in a speech to the World Economic Forum in Davos in January.

According to the newspaper, “Definers pressed reporters to explore the financial connections between Mr Soros’s family or philanthropies and groups that were members of Freedom from Facebook, such as Color of Change, an online racial justice organization, as well as a progressive group founded by Mr Soros’s son.”

Elliot Schrage, Facebook’s outgoing head of communications and policy, said: “We asked Definers to do what public relations firms typically do to support a company — sending us press clippings, conducting research, writing messaging documents, and reaching out to reporters.

“Some of this work is being characterized as opposition research, but I believe it would be irresponsible and unprofessional for us not to understand the backgrounds and potential conflicts of interest of our critics.”

He added, however, that “in January 2018, investor and philanthropist George Soros attacked Facebook in a speech at Davos, calling us a ‘menace to society’ We had not heard such criticism from him before and wanted to determine if he had any financial motivation. Definers researched this using public information.

“Later, when the ‘Freedom from Facebook’ campaign emerged as a so-called grassroots coalition, the team asked Definers to help understand the groups behind them. They learned that George Soros was funding several of the coalition members. They prepared documents and distributed these to the press to show that this was not simply a spontaneous grassroots movement.”

He said Facebook had not asked Definers to distribute or create fake news.

An official at Mr Soros’s Open Society Foundation told the New York Times that while the philanthropist had given to funds to two of the groups which were part of the “Freedom from Facebook” coalition, no grants had been made to support campaigns against Facebook.