Danish energy merger under fire.

Byline: Patricia Koza

An influential report due out next week by the Organization for Economic Cooperation and Development criticizes a proposed $5 billion merger between Denmark's two biggest energy companies and could raise new doubts about the deal.

The OECD, the group of the world's 30 richest countries that advocates market economics and is best known for its reports and statistics, can't directly interfere with the merger between state-owned Danish Oil and Natural Gas A/S, or Dong, and electrical utility Elsam A/S.

But its weighty opinion could embolden opponents to the deal and tip the balance in favor of Swedish power giant Vattenfall AB, …