JERUSALEM (Reuters) - Israel may ban from trading on the Tel Aviv Stock Exchange companies whose main business revolves around bitcoin and other cryptocurrencies, the Israel Securities Authority (ISA), the country’s markets regulator, said on Thursday.

FILE PHOTO: A copy of bitcoin standing on PC motherboard is seen in this illustration picture, October 26, 2017. REUTERS/Dado Ruvic/File Photo

The regulator has proposed an amendment to exchange rules that would prohibit it from listing shares issued by companies that mainly invest in, own or mine cryptocurrencies. Such companies also would not be allowed in the exchange’s indexes, and if they already trade on the exchange they would be delisted.

The ban would not apply to companies with equity of more than 100 million shekels ($29 million) and with three years of audited financial statements.

The amendment has been approved by the ISA board and next goes for public comment.

The proposal for the amendment came after a sharp rise in shares of Blockchain Mining BLCM.TA, a company that said it would shift its focus from mining for gold and iron to mining crypto currencies.

“This phenomenon, if it continues, may in the future have serious consequences on the ... fairness of trading in the bourse in general and on investor confidence in the bourse,” the ISA said.

Share prices of companies intending to operate in the sector are cut off from their real value, the ISA said, and “the market treats their shares irrationally and unexpectedly.”

Last month, outgoing ISA chairman Shmuel Hauser said he planned to bring such a proposal up, saying bitcoin prices were behaving like a bubble.

The value of a bitcoin, the biggest and best-known cryptocurrency, surged in mid-December to nearly $20,000, then dropped to less than $12,000 at the end of the month. It was trading today around $14,500.

Bitcoin is a publicly available ledger of a finite number of digital “coins”, which backers say can be used as a currency without the support of any country’s central bank. It is “mined” by computers, which are awarded new coins for working out complex mathematical formulas. Several other cryptocurrencies have also been launched that work on similar principles.

($1 = 3.4453 shekels)