Energy giant Royal Dutch Shell is "in talks" to buy gas utility BG Group, the Wall Street Journal has reported, citing "people familiar with the matter".
The mega-merger could produce a company with a combined market capitalisation of more than £200bn ($296bn; €274bn).
A Shell spokesman told the BBC: "We're not making any comment."
No-one from BG Group was immediately available to confirm or deny the WSJ's report.
If the deal goes ahead, the recent collapse in oil prices will have played a large part in it.
BG Group, Britain's third largest energy company, said in February that it would write down the value of its oil and gas assets by nearly £6bn ($9bn) due to the oil price slump.
Similarly, Shell announced in January that it would be cutting spending by nearly £10bn over the next three years.
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