Cryptocurrencies like bitcoin and the banks and financial firms that trade them need to be more closely regulated, one of the ECB's top policymakers has said. 

Officials from the world's top economies are set to discuss the impact of digital currencies at next month's G20 meeting in Argentina.

They are expected to signal a more coordinated approach to their regulation. 

"Any virtual currency business of credit institutions needs to be rigorously supervised to ensure that risks emerging from such activities are contained," ECB Executive Board member Yves Mersch said.

Yves Mersch said that proper protocols were needed to meet anti-money laundering and counter terrorist financing regulations. 

"Furthermore, given the risks posed by leverage, credit institutions should not accept virtual currencies as collateral by banks," he added. 

Mersch is the latest of a slew of global policymakers to speak out against digital currencies after their meteoric rise last year. Bitcoin, the best-known crypto asset, rose more than 1,000% in 2017.

This year, however, the threat of regulatory clampdowns and bans from credit card firms to social media sites, has already caused it to tumble about 50%. 

In the same vein, relevant market authorities should also monitor, analyse and regulate Initial Coin Offerings (ICO) - where companies or projects issue their own digital coins or 'tokens' as a way of raising real world money from the public. 

In 2016, the total amount of funds raised through ICOs was less than €82m. This number dramatically increased to over €3 billion in 2017. 

Despite the concerns he raised, Mersch said that the ECB was looking at its own virtual currency, although he stressed it would be more of a digital version of cash rather than a bitcoin-styled revolution. 

Central banks already create money digitally via the reserves that banks either park or borrow, but that is not technically the same as the money that comes out of cash machines and used for everyday payments. 

Any new digital currency would be like that though. At the same time however its use would depend on its popularity. 

"One could imagine a digital representation of cash that replicates the features of cash in the reasonably distant future, if citizens demanded it," the ECB's Mersch said. 

Mersch acknowledged that negative interest rates, like those currently at the ECB, were part of the virtual currency debate. 

Economists argue having these currencies would allow central banks to slash rates even further as people and firms would then not be able to withdraw and stash away physical cash to avoid the hit of sub-zero rates to their savings. 

However "deeply negative" rates would not become a standard instrument in the central bank's toolbox, Mersch said.