The International Petroleum Exchange is this week poised to call a long-awaited extraordinary general meeting to vote on new plans to demutualise Europe's largest energy derivatives marketplace.

The decision, which is likely to follow a regular meeting of the board on Thursday, will mark the final phase in a tortuous and controversial tussle over ownership. The wrangle forced the resignation of the exchange's former chairman and chief executive and prompted the intervention of City watchdogs. Under the new plan, exchange ownership and the right to deal on the trading floor, hitherto inextricably linked through its arcane membership system, will be separated for the first time. Holders of the derivatives market's 70 seats, currently valued at around £115,000 each, will receive new trading rights as well as a number of shares, yet to be decided. Both the trading rights and the shares will then be separately transferable, subject to board approval. The new proposal, which follows a period of intense consultation, marks the IPE's second attempt at demutualisation. Last summer, a plan to sell a 70% majority stake to a consortium of outside investors, including Enron and British Gas, narrowly failed after the then management team failed to secure majority approval. The Financial Services Authority stepped in after the chairman, Lord Fraser of Carmyllie and chief executive Lynton Jones subsequently resigned.