CALGARY, Alberta - M&G Investment Management Ltd, the largest shareholder in Gibson Energy (GEI.TO), on Monday urged the Calgary-based oil and gas infrastructure company to launch a strategic review process to cut costs and boost returns.

London-based M&G, which owns 19.4 per cent of Gibson's outstanding shares, released an open letter laying out its views of the company and the steps it could take to maximize value, including being sold.

Gibson Energy, which provides storage and transportation services to energy companies across North America, has been hard hit by the prolonged slump in global crude prices. Its share price has slumped more than 55 per cent since late 2014.

Monday's letter, signed by M&G's Global Dividend Fund manager Stuart Rhodes, said the fund had been trying to apply "significant pressure" on Gibson's management for over two years to spur change but it was disappointed by the pace of progress.

"It is clear to us when we communicate with industry analysts, the company's competitive peer group and other investors that there is confusion around the long term strategy for the company," Rhodes wrote.

Gibson should focus on its terminals in the Alberta storage hubs of Edmonton and Hardisty, and sell off its 19,000 barrel per day Moose Jaw, Saskatchewan, refinery and all parts of its trucking business not associated with core assets, the letter said.

M&G said it also wants Gibson to make significant progress in reducing its cost structure before commencing a strategic review process with the help of an independent investment bank.

"We believe that a streamlined and focused company based around core strategic assets would be an attractive asset to a wide variety of potential suitors," the letter said.

"If the market is not going to give the company the appropriate valuation we think it deserves, then we are confident the value can be realized by a sale process."

Earlier this month Gibson said it will sell off its U.S. environmental business to concentrate on operations in western Canada, a move welcomed by M&G, which said it did not have the strategic footprint or cheap enough access to capital to compete south of the border.

The company named a new chief executive in June, with Steve Spaulding replacing Stew Hanlon.

In an email response to a request for comment, Gibson said it was aware of M&G's letter and would provide a response shortly.