A push by 11 European countries to create a tax on financial transactions hit a major obstacle Tuesday, as European Union lawyers suggested the plan could breach EU rules in several ways.

The proposal, which has already suffered long delays and been shunned by most of the EU's 28 member states, would see levies of 0.1% applied to share and bond trades and 0.01% to derivative transactions between financial institutions if at least one party were located in the EU.