"I certainly suggested that Berkshire look at investing in something that the Mungers were already invested in, but we'd been in it for years," he said in a phone interview.

The Munger investment was cited last week by former Berkshire manager David Sokol in a CNBC interview as precedent for his purchase of Lubrizol Corp. shares before recommending the company as a takeover target to Buffett.

Sokol, whose resignation from Omaha, Nebraska-based Berkshire was announced by Buffett on March 30, said there was nothing unethical about purchasing about 96,000 Lubrizol shares in January.

"I don't believe I did anything wrong," Sokol said, according to a transcript on CNBC's website. "Mr. Munger owned a significant piece of BYD before he mentioned it to me to go look at it."

Munger, 87, said his family invested with money manager Li Lu in BYD through a partnership that has a stake of about 3 percent and that he urged Sokol, then the leader of Berkshire's energy business, to scout the business.

"I had Dave look at it, because I knew I couldn't talk Warren into buying into the damn thing by myself," Munger said. "It's a new technology-type investment. But David went over there, and he made the deal for Berkshire." Buffett is Berkshire's chairman and chief executive officer.

Berkshire's investment
Berkshire invested $230 million in BYD in 2008 and holds a stake of almost 10 percent in the company. The investment was valued at $1.18 billion at the end of 2010, Buffett said in the company's annual report. BYD, based in Shenzhen, has said it aims to begin selling electric and hybrid cars in Europe by the end of next year.

Munger said his family holds a "little more" than half of the fund with the BYD investment, and that he didn't participate in Berkshire's discussions on its deal. "I recused myself," Munger said. "But there's no question about it, that I caused Dave's original interest." He declined to comment further.

The Munger investment in BYD is different from Sokol's in Lubrizol because of the longer amount of time that elapsed before Berkshire announced its intention to acquire shares, said James Cox, a professor of corporate and securities law at Duke University Law School in Durham, North Carolina.

"What really matters is the close time sequence that we all now know that Sokol made the investment," he said.

The Securities and Exchange Commission is probing whether Sokol, 54, bought shares in Lubrizol on inside information that Berkshire was considering buying the company, according to a person who declined to be identified because the investigation is secret.

Buffett didn't immediately respond to a message left with an assistant for comment.