France and Germany's economy chiefs and senior central bankers have collectively called for a crackdown on Bitcoin and similar cryptocurrency as its price continues to swing.

Digital coins "could pose substantial risks for investors" and should be monitored closely, they claimed in a letter addressed to fellow G20 finance ministers.

The letter, which requested that a discussion surrounding regulation was chalked onto the agenda for this year's G20 Summit, was signed by German interim finance minister Peter Altmaier and France's Bruno le Maire.

It read: "Tokens and their potential for financial innovation should not be left to those who make the worst use of them. France and Germany have already taken concrete regulatory measures regarding 'virtual currencies' in the field of anti-money laundering and counter-terrorism financing and the European Union is working in the same direction.

"However, an efficient pushback against the use of “tokens” and “virtual currencies” for the purpose of criminal activities will require a coordinated international effort."