London investment banks and energy traders joined counterparts elsewhere in Europe in voicing concern over a plan by the European Commission to subject the trading of energy as well as gas and electricity derivatives to tougher regulation.

The measures are expected to form part of Brussels' sweeping package to overhaul the European Union energy market, most importantly by forcing integrated energy companies to divest infrastructure assets such as pipelines and power grids. However, a little-noticed plan that would force energy traders to comply with stricter post-trade transparency and reporting requirements has alarmed the financial services industry.