BG Group Plc’s (LON: BG) CEO Chris Finlayson resigned after little more than a year in the job as the third-largest U.K. oil and gas producer ditched an output forecast that’s just three months old. BG Group operates in the Marcellus and Haynesville Shales in the United States, and also operates elsewhere.

Finlayson will be replaced immediately by chairman Andrew Gould until a permanent successor is found, BG said April 28 in a statement. Its shares dropped the most since January.

BG said April 28 oil and gas output this year would be at the lower end of an estimated range on falling production in Egypt. The company is reviewing operational, investment and portfolio management plans and won’t offer 2015 guidance until February, it said, abandoning a forecast Finlayson made in January.

“The board felt that it was in the best interests of the group to accept Chris’s resignation and seek fresh leadership,” said Gould. BG needs to accelerate returns to shareholders, he said. The company said Finlayson resigned for personal reasons.

BG slid as much as 6.8% to 1,067.5 pence, the biggest intraday decline since the outgoing chief unveiled project delays on Jan. 27. The stock was down 3.1% at 1,109 pence by 10:42 a.m. in London.

Finlayson, a former Royal Dutch Shell Plc (NYSE: RDS-A, RDS-B) executive who joined BG in 2010 before taking over from long-term CEO Frank Chapman at the start of last year, was forced to issue a profit warning in January because of delays at projects in Australia, Brazil and the North Sea, as well as political turmoil in Egypt. The shares dropped 14% that day.

“Only two and a half months ago he was still confirmed in the job, obviously frustrated by Egypt, and seemed to be the savior of BG a year ago,” said Jason Kenney, an analyst at Banco Santander SA in Edinburgh. “The surprise resignation could be seen as a reaction or a frustration that a growth period for BG is struggling to get started.”

The Reading, England-based company will report its first-quarter earnings on May 1.

Egyptian oil and gas production dropped 35% in the first quarter, to 66,000 barrels of oil equivalent a day from the prior three months because of deteriorating reservoir performance and the diversion of fuel to the domestic market, BG said. That means total output for 2014 will be at the lower end of its forecast of 590,000 to 630,000 barrels a day (bbl/d).

In January, BG had said 2015 production would be 710,000 to 750,000 bbl/d as new fields started output.

“Egypt has further deteriorated,” said Bertrand Hodee, an analyst at Raymond James Financials Inc. in Paris, cutting his output forecast 4.6% to 587,000 bbl/d this year.

Finlayson was charged with balancing record capital spending with lower-than-expected oil and gas production after taking over from Chapman. BG shares rose 28% last year under his leadership before plummeting this year following the January profit warning and April 28’s resignation.

BG, formed in 1997 when former state gas monopoly British Gas Plc split its exploration and production arm from its retail business, is the biggest U.K.-listed gas producer after Royal Dutch Shell Plc and BP Plc. (NYSE: BP). Chapman was CEO from 2000 to 2012.