Bank of Canada says it's an option in case of "shock" to economy

$7 trillion of government-issued debt now has below-zero returns

Negative interest increasingly blamed for market panic

Interest rates in Canada today are among the lowest this country has ever seen, but a growing number of experts say they’re going to come down even further — all the way to below zero.

Canada is most likely to be the next country to chop its key lending rate below zero, says Marc Chandler, head of foreign exchange strategy at financial services firm BBH.

"I am not saying the Bank of Canada will, but that is the most likely candidate of those that are not there yet,” Chandler told CNBC on Friday.

A new report from Citigroup doesn’t think Canada will be the next country to pull the trigger on negative rates (it nominates Israel instead), but says Canada is among a small group of countries that could go below zero in the next two years.

“In the Czech Republic, Norway and perhaps Canada, a negative policy rate is not part of our central scenario, but the risk of a negative policy rate is material,” Citigroup economists wrote, as quoted at the Financial Post.

Central banks go negative when inflation is very weak or nonexistent, meaning the economy is stagnating. When a central bank sets its interest rate below zero, it means it’s charging commercial banks to keep their cash there. In theory, this should convince banks to lend more, instead of holding cash, helping to spur the economy.