The US government has won a civil forfeiture case against Megaupload founder, Kim Dotcom after he was barred from contesting the seizure of his assets.

Now an estimated $67m (£45m) of Dotcom's assets – including cash, luxury cars, art, jet skis and TVs – belong to the US government.

Dotcom's New Zealand property was raided in 2012 and US and New Zealand authorities seized millions of dollars in cash and assets. The US government contends that the assets were obtained illegally, through copyright-related crimes and money laundering.

Megaupload.com was shut down by the FBI in January 2012 and charges were pressed against the online entrepreneur the following month.

Criticising the judgement by District Court Judge Liam O'Grady, Dotcom said: "By labelling me a fugitive the US court has allowed the US government to legally steal all of my assets without any trial, without any due process, without any test of the merits.

"The asset forfeiture was a default judgement. I was disentitled to defend myself."

Dotcom has been on bail since 2012 and is fighting US charges in relation to online piracy, but the German-born businessman has continually claimed his innocence and vowed to appeal the decision.

"For the first time we get the opportunity to test the decisions of this judge at a higher court. Because of the way his previous rulings were designed he made an appeal impossible. But we now can and probably will appeal O'Grady's decision on fugitive disentitlement and forfeiture," Dotcom said.

"First the US judge ruled that I can't mount any defence in the asset forfeiture case because according to him I'm a 'fugitive'", he said.

"Think about that for a moment. I have always said that I'm innocent. There was no conspiracy. I have done nothing wrong."

Things are set to get even tougher for Dotcom and the other defendants in the Megaupload case who will face an extradition hearing in June, after Dotcom's request to postpone the hearing was rejected earlier this week.