BUDAPEST (Reuters) - Hungarian Prime Minister Viktor Orban on Friday said it was high time the European Union reconsidered the basic parameters binding it together, then revamp its founding treaties, or face political radicalization across the continent.

Orban has been at odds with Brussels ever since coming to power in 2010, and recently became an outspoken critic of the EU's handling of the migration crisis and other challenges.

Asked about a Dutch proposal to create a tighter core in the EU with external passport controls, dubbed a "mini-Schengen", Orban said not only Schengen but other aspects of the EU were ineffectual today and needed to be reformed.

He said the migration crisis and heightened risk of terrorism made new security and border control regulations necessary, and the recent euro zone crisis forced questions about a joint monetary policy without a common fiscal policy.

"Several things that happened in the past six to seven years prompt European leaders to rethink basic aspects of European politics," Orban said in an interview with Hungarian public radio.

"It is highly likely that then we will have to adjust the fundamental treaties of the EU. The Schengen treaty begs for correction. If you think back to the Greek financial crisis and the answers we gave to that, the situation is the same."

The lack of coordinated fiscal policy to support joint monetary policy in the euro zone probably also called for amendment to EU treaties, he said.

"If we want to step up against the terrorism threat, again we need to do the same. If we don't want immigration to erode public safety then we need new rules. I think the time has come to ask the basic questions of the European Union once again."

He said after last week's Paris attacks by Islamist gunmen, some of whom were believed to have traveled to fight in Syria, there was no reason to doubt that there was link between immigration and terrorism, even if EU leaders were reluctant to accept it.

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If the bloc did not face up to facts, voters would turn to parties that do, Orban said.

"Under such circumstances support keeps growing for radical, extremist, off-mainstream political forces that question the current European system but call a spade a spade."

"We must not stop speaking the truth to the radical parties because voters will follow those who speak the truth and European politics will grow more radical, which is in nobody's interest."

Orban's own Fidesz party remains by far the most popular in Hungary, with the radical right-wing Jobbik party its strongest opposition.

(Reporting by Marton Dunai; Editing by Dominic Evans)