LONDON, April 16 (Reuters) - The principles of openness and universal access that underpinned the Internet's creation are facing their greatest-ever threat, the co-founder of Google Sergey Brin said in an interview published by Britain's Guardian newspaper on Monday.

Brin said the threat to freedom of the Internet came from a combination of factors, including increasing efforts by governments to control access and communication by their citizens.

Brin said attempts by the entertainment industry to crack down on piracy, and the rise of "restrictive" walled gardens such as Facebook and Apple, which tightly control what software can be released on their platforms, were also leading to greater restrictions on the Internet.

"There are very powerful forces that have lined up against the open Internet on all sides and around the world," Brin was quoted as saying. "I am more worried than I have been in the past. It's scary."

He said he was concerned by efforts of countries such as China, Saudi Arabia and Iran to censor and restrict use of the Internet.

Brin said the rise of Facebook and Apple, which have their own proprietary platforms and control access to their users, risked stifling innovation and balkanising the web.