The founder of failed Bitcoin exchange Mt. Gox will not travel to the US to face questions about its collapse into bankruptcy, according to his lawyers.

Mark Karpeles, who founded the world’s biggest cryptocurrency exchange, has rejected a subpoena by a Dallas court demanding his presence to answer enquiries over how Mt. Gox lost an estimated 750,000 bitcoins earlier this year.

The founder is currently in Japan, and a filing by his lawyers said he is "not willing to travel to the US".

It read in full: "Mr. Karpeles is now in the process of obtaining counsel to represent him with respect to the FinCEN Subpoena. Until such time as counsel is retained and has an opportunity to ‘get up to speed’ and advise Mr. Karpeles, he is not willing to travel to the U.S."

A further summons by the US Treasury’s Financial Crimes Enforcement Network was not specific about what topics would be up for discussion, the lawyers added.

Karpeles has not been charged with any offences since Mt. Gox went bankrupt.

The exchange was shut down in February after a loss of around $350m, which precipitated a steep drop in the value of Bitcoin.

The lost coins amount to around 6% of the overall 12.4m bitcoins currently in circulation, and it remains unknown whether customers will have their bitcoins recovered.

However, an old wallet – thought to be redundant – was recently found to contain 200,000 bitcoins, reducing the total missing bitcoins to 650,000.