As if liner shipping did not have enough problems already, there is a new one emerging.

Push-back against the potential implications of the rapid — although long-expected — round of mergers and new alliances seen in the past 18 months appears to be gaining momentum.

This week, it was the United Nations Conference on Trade and Development (Unctad)'s turn to wade into the debate with a warning over the risks of lines holding oligopolies on routes to the detriment of shippers, consumers and nations.