Nov. 28 (Bloomberg) -- Macquarie Group Ltd., Australia’s biggest investment bank, said Chairman David Clarke will take leave for six months to undergo treatment for cancer.

Kevin McCann will be acting chairman in Clarke’s absence, the Sydney-based company said in a statement to the stock exchange today. Macquarie didn’t provide more details.

Clarke, 66, who has been chairman at Macquarie since the bank was formed in 1985, was also a director at the company’s predecessor, Hill Samuel Australia Ltd., from 1971. He ceased executive duties at Macquarie in March 2007.

Chief Executive Officer Nicholas Moore posted a smaller- than-expected 43 percent drop in first-half profit on Nov. 18 and said earnings may withstand the credit crunch. Moore forecast profit “broadly in line with the first half” for the remainder of the year through March, reassuring investors after Macquarie’s stock dropped to a six-year low this month.

Macquarie’s shares fell 1.1 percent to A$29.23 at 2:06 p.m. in Sydney today, compared with a 1.6 percent gain in the 46- company S&P/ASX 200 Finance Index.

Clarke, who obtained an MBA from Harvard University in 1966, is also chairman of Sydney-based Goodman Group, Australia’s biggest industrial real estate investment trust, and Australian Vintage Ltd.

He serves on the Asia Advisory Board of Bloomberg LP, the parent of Bloomberg News.

To contact the reporter for this story: Stuart Kelly in Sydney skelly22@bloomberg.net

Last Updated: November 27, 2008 22:09 EST