Another Silicon Valley billionaire has left California, adding to growing fears that the state's wealthiest residents are taking their money elsewhere over a proposed tax to the ultra-rich.

Google co-founder Sergey Brin, 52, moved a significant portion of his businesses out of the state in the days leading up to Christmas.

That included 15 limited liability companies based in California related to the billionaire's business interests and investments, The New York Times reported.

Seven of those companies were re-registered in Nevada, including entities linked to the management of a super-yacht and an interest in a private terminal at San Jose International Airport.

Another entity affiliated with Brin also moved its registration to Nevada on Christmas Eve.

Brin is the fourth richest person in the world today and is valued at $248.2billion, according to Forbes.

He still owns multiple homes in California, according to the Times, but how much time he will spend in the state this year is unknown.

Seven of Brin's limited liability companies previously based in California were recently re-registered in Nevada

Pictured: Menlo Park suburb looking out to Palo Alto in Silicon Valley

Brin's move away from California comes after his Google co-founder Larry Page also cut ties with the state late last year.

Page transferred most of his business holdings to Delaware, according to Business Insider. He also incorporated some of his ventures in Florida.

Brin is thinking about buying a home in Miami, the Wall Street Journal reported.

Both men founded Google - based in Mountain View, about 45 miles south of San Francisco - in 1998 after meeting at Stanford while studying computer science.

They stepped down from Alphabet Inc, Google's parent company, in 2019.

The cofounders' decision to flee the west coast comes as a proposed billionaires' tax that would target California residents worth more than $1billion looms on the horizon.