Former White House chief strategist Steve Bannon has deep ties to the embattled data firm, Cambridge Analytica, which has come under scrutiny for using the Facebook data of 50 million people without permission.

Bannon, who helped found the data company and served as its vice president, has denied knowing about the firm's purchase of the Facebook data.

But a former employee at the company contradicts Bannon's claims and recently posted a page from an alleged letter indicating that Bannon was, at least in part, aware of Cambridge Analytica's activities related to the US election.

Former White House chief strategist Steve Bannon distanced himself this week from the data firm Cambridge Analytica amid an outcry over its misuse of Facebook data, which compromised the personal information of roughly 50 million users.

Bannon, the former head of President Donald Trump's campaign, said he "doesn't remember" buying the data, even though he was serving on the firm's board at the time. He instead blamed "the Cambridge guy," referring to former Cambridge University professor Aleksandr Kogan, the researcher at the center of the scandal.

“I didn’t even know about the Facebook mining,” Bannon said during a conference hosted by The Financial Times in New York on Thursday. “That’s an issue between Cambridge [Analytica], the professor, and Facebook.”

But former Cambridge Analytica employee Christopher Wylie, who oversaw research at the company at the time it acquired data from Facebook, disputes that assertion.

In an interview with The Washington Post, Wylie said Bannon"approved the data-collection scheme we were proposing" and even had authority over the company's CEO Alexander Nix.

“We had to get Bannon to approve everything at this point," Wylie continued. "Bannon was Alexander Nix’s boss. Alexander Nix didn’t have the authority to spend that much money without approval.”

The acquisition of Facebook data cost the firm nearly $1 million, according to The Post.

Wylie doubled down on his claims in a tweet on Friday, saying "Bannon knew" about the firm's activities, particularly as it relates to its work during the US election. The tweet was accompanied by a photo of what appears to be a July 2014 letter from former New York mayor Rudy Giuliani's law firm addressed to Bannon, Nix, and Rebekah Mercer, the conservative megadonor who helped finance the company.

The letter appears to have been sent in response to a request for guidance regarding "the participation of Cambridge Analytica, LLP, a foreign corporation, and of foreign nationals in connection with United States elections for federal, state and local government office."

The law firm said it would first explain the law, the regulations and other "relevant precedents" before offering guidance.

It began by saying that US law currently prohibits "contributions, donations, expenditures, independent expenditures, and disbursements by foreign nationals," and added that "of greater concern" was the "participation by foreign nationals in decisions involving election-related activities."

Wylie’s tweet included only the first page of the alleged letter. It is not publicly known what else was contained in the document with regard to specific guidance.

Although it's unclear whether Bannon knew exactly how the data was collected, it appears unlikely, given the extent of his involvement with Cambridge Analytica, that he was completely unaware of the purchase of Facebook data.

Bannon was one of the key players involved in the formation of the firm in 2013.

During Thursday's conference in New York, he even bragged that he coined the name of the company.

"It's a stroke of genius," he said.

From June 2014 until he signed on to lead the Trump campaign in August 2016, Bannon served as Cambridge Analytica's vice president. Trump would later hire Bannon to serve as his chief strategist in the White House.

The Trump campaign hired the data analysis firm to lead its digital advertising efforts in June 2016.

Cambridge Analytica has come under fire in the last week since reports disclosed how the firm harvested the information of 50 million Facebook users without permission and used that data to target them with personalized political ads.

Facebook CEO has since apologized for what he described as "a breach of trust." The social media platform has suspended Cambridge from buying ads or using its services and Alexander Nix has been suspended amid an investigation by British lawmakers into the company's practices.