BRUSSELS, Feb 17 (Reuters) - Establishing a single record of trading data from the dozens of separate national exchanges and trading venues is a priority in its current review of markets rules, the European Commission said on Monday.

The mechanism, known as a "consolidated tape", has been a longstanding goal for investors in Europe, which has about 20 trading venues. Some offer the same stocks but publish information on trades and volumes in different ways.

Although EU markets rules, known as MiFID 2, created the legal framework for the consolidated tape, no provider has so far emerged.

Its creation is now the first priority of the Commission in its review of the rules, the EU executive said on Monday in a document that began a public consultation on the overhaul of MiFID II, which has been in force since 2018.

"A European consolidated tape could be one major step towards 'democratising' access to 'market data' so that all investors can see what the best price is to buy or sell a particular share," the Commission said.

The measure would also help brokers to locate liquidity at the best price available in the European markets, and make it easier to evaluate their broker's performance in executing an order, the commission said.

It is asking governments, experts and market players what are the main reasons a consolidated tape has yet not emerged in Europe. The consultation, which is open until April 20, is expected to be followed by legislative proposals.

If created, a single record of real-time trading data would mirror a system adopted in the United States decades ago to bolster efficiency in trading by knitting together platforms.

The Commission said that its other priorities in the MiFID II review are changes to rules on investor protection, the review of regulations on unbundling research and other financial services, and reforms to foster more commodity derivatives trading denominated in euros.

(Reporting by Francesco Guarascio @fraguarascio) ((Francesco.Guarascio@thomsonreuters.com; +32 2 287 68 17;))