The European Central Bank is paying close attention to bitcoin | Jack Guez/AFP via Getty Images How Europe is bursting bitcoin’s bubble Continental policymakers join chorus of concern.

Europe's financial watchdogs are turning the screws on bitcoin and its cryptocurrency pals, helping to let the air out of a price boom that many economists warn is a bubble.

Over the past year Europe's financial regulators watched cautiously as bitcoin's price soared nearly to $20,000, lifting other cryptos in its wake.

But the grace period is coming to an end as Europeans join policymakers from around the world in warning about a possible bubble that could punish regular investors if it pops.

The increased scrutiny coincides with a leveling of bitcoin's price, quoted Friday at $11,841 (€9,652), down from a high of nearly $20,000 at the end of 2017, but still up from about $1,000 at the start of last year.

French Finance Minister Bruno Le Maire is among the most vocal advocates for regulation.

Paris wanted to “avoid the risks of speculation or possible financial traffics linked to bitcoin,” he said earlier this week, after appointing former central bank Deputy Governor Jean-Pierre Landau to lead an investigative mission on cryptocurrencies and how they might be regulated.

In his efforts to tame bitcoin, Le Maire is getting plenty of backing from the European Commission.

In December, Valdis Dombrovskis, the Commission vice president responsible for financial services, wrote to the EU’s three financial watchdogs urging them to warn investors about a possible bubble and puncture the hype surrounding cryptos.

He also asked them to review the EU's regulatory framework to see whether it is suitable for bitcoin, citing “clear risks for investors and consumers associated to price volatility.”

On Wednesday, a spokesperson for the Commission said it is continuing to follow developments on cryptocurrencies “very closely.”

In the spring, the EU’s executive arm is set to present an action plan on financial technology that will include policy recommendations on the use of blockchain technologies which underpin bitcoin — as well as cloud-data servicing and online security.

While the European Supervisory Authorities are yet to take action, they’re not mincing their words when it comes to cryptocurrency.

Steven Maijoor, chairman of the European Securities and Markets Authority, said in an interview with Bloomberg that investors “should be prepared to lose all their money” if they choose to invest in bitcoin.

“It has an extremely volatile value, which undermines its use as a currency,” he added. “It’s also not broadly accepted.”

On Thursday, ESMA confirmed it was looking into curbing spread-betting through potential product intervention measures. ESMA’s consultation looks into leverage limits for so-called contracts for difference (CFDs), and the watchdog is also considering whether CFDs in cryptocurrencies should be addressed in the measures.

The U.K.’s Financial Conduct Authority has issued similar warnings, for example on initial coin offers — a way to raise funds where issuers accept a cryptocurrency, like bitcoin, in exchange for a token that represents something related to a firm or project such as a share or some kind of future service. The product, which is banned in China, comes with a “good chance of losing your whole stake,” the U.K. regulator cautioned.

The European Central Bank is also paying close attention to bitcoin.

ECB President Mario Draghi has stated that cryptocurrencies are beyond the mandate of the central bank — but that there is merit in examining developments more closely.

Addressing the European Parliament in September 2017, he said: “Our main worry with these innovations … is the potential fragility with respect to cyber risks. That’s where we really are focusing our work now.”