A month and a half after announcing his plan to move from the Federal Trade Commission to the White House Office of Science and Technology Policy, a failed background check is forcing Ashkan Soltani to leave government.

The former FTC chief technologist was slated to join OSTP as a senior adviser to Federal CTO Megan Smith, however Soltani was told last week he would not be granted the necessary security clearance to work at the White House.

Soltani announced the "bittersweet" news in a tweet on Jan. 29, first reported on FCW.com.

Followers on Twitter were quick to respond with their dismay and any number of theories as to why Soltani was denied, including his work with the Washington Post, Wall Street Journal and other news outlets investigating government surveillance programs and other privacy issues.

For his part, Soltani declined to speculate.

"I'm told this is something that happens from time to time and I won't speculate on the reasons," he said in a letter accompanying the tweet. "I passed the mandatory drug screening some time ago and the FBI background check was still underway. There was also no allegation that it was based on my integrity or the quality of my work."

Soltani was appointed to the White House post on Dec. 16 to advise the CTO on the ethical issues around privacy and big data and help engage with technologists, both in the private sector and by encouraging more to sign up for public service.

"Those are vital issues, which have occupied me in and out of government, and I will continue to contribute what I can in other venues," he said. "I was honored to serve at the FTC and in the White House. I wish the CTO and her amazing team success in the important work ahead."