WASHINGTON — Oil leaking from a BP well in the Gulf of Mexico could increase as much as 12 times to 60,000 barrels a day if the company fails to stem the flow, Representative Edward J. Markey, Democrat of Malden, said yesterday after a briefing by industry executives.

“The amount of oil per day could actually rise from 5,000 to 60,000 barrels,’’ said Markey, who held a closed-door meeting with executives from BP and other oil companies and members of the House Energy and Environment subcommittee, which he chairs.

Representatives from Transocean Ltd., owner of the well, and Halliburton Co. attended the meeting to discuss how the companies intend to cap and contain the oil leak.

“They indicated to us that they do believe they have a possibility of being successful, but they are not guaranteed,’’ said Markey. “It’s pretty clear that there was not proper preparation for the worst-case scenario.’’

A BP spokesman said he didn’t have any worst-case data and couldn’t comment.

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