Greece is heading for default, or at least a devaluation, and European Union (EU) leaders have to adopt a "plan B" to stem contagion to the rest of the bloc, billionaire investor George Soros said Tuesday.

"Greece is heading towards disorderly default and/or devaluation ... A Greek default may be inevitable but it need not be disorderly," he wrote in an editorial for the Financial Times.

"While some contagion ... will be unavoidable, the rest of the euro zone needs to be ringfenced. That means strengthening the euro zone, probably by wider use of Eurobonds and a euro zone deposit insurance scheme," he said.

He also reiterated his call for European policymakers to come up with a "plan B" to muster the political support needed to take such measures and said that Europe's elite had to "revert to the principles that guided the union's creation."

Soros, famous for making $1 billion by betting against the British pound in 1992, said in June that it was "probably inevitable" that a country would exit the euro without naming a specific country.

At a Monday meeting in Brussels, euro zone finance ministers stressed their determination to resist contagion by examining how to help Greece but declined to rule out the possibility of a selective default by the country.

Meanwhile Soros also said the European status quo has become untenable, yet it should still be possible to mobilize a “silent majority” in favor of further advance toward a united Europe,

Soros said the euro was from the start an incomplete currency, in the sense that it had a central bank but no treasury, and its architects thought, wrongly, that markets would correct their own excesses; hence they set up rules designed to stop only public-sector excesses.

The excesses, however, were mainly in the private sector, as interest-rate convergence generated economic divergence; lower rates in the weaker countries led to housing bubbles, while the strongest country, Germany, had to keep a tight rein to cope with reunification; and finance was compromised by the spread of risky financial instruments and unsound lending practices, Soros said.

As integration has turned into disintegration, Europe’s political establishment has turned from spearheading further unification to defending the status quo, he said.