The Investment Industry Regulatory Organization of Canada (IIROC), the country's main investment industry self-regulator, said on Thursday it is taking another look at the rules, which it withdrew after criticism from the financial industry.

It is again seeking industry comments, with a deadline of March 30.

In non-transparent markets, often called dark markets or dark pools, buyers and sellers interact directly and trades occur without quotes or shares being displayed on exchanges in real time.

The proposed IIROC rules, called anti-avoidance rules, would bar trading orders from leaving Canada for execution on markets where order information is not displayed, or when the exit would not result in meaningful price improvement for the customer.

"We believe that Canadians should get the best possible price, but the price improvement must be sufficiently meaningful to forgo the benefits that transparency brings to Canada and to the quality of Canadian markets," IIROC Chief Executive Andrew Kriegler said in a statement.

The move aims to offset the ability of wholesale brokers in the United States to pay cash to win Canadian order flow. These brokers often operate in dark markets. Payment in return for order flow is not permitted in Canada.

While U.S. rules mandate disclosure when broker-dealers pay for order flow, Canada does not seek the same disclosure from firms receiving payment for routing their orders to U.S. wholesale brokers.

TMX Group, operator of the Toronto Stock Exchange, cited the exodus of orders to the United States as a major impetus for last year's announcement of a plan to offer rebates for active order flow on its smaller Alpha exchange.

U.S. venues that trade in Canadian securities say that higher fees charged by Canadian banks and brokers are more to blame for the southward flow of trades than the cross-border regulatory discrepancy.

(Reporting by Alastair Sharp; Editing by Peter Galloway)

By Alastair Sharp