Aug 2 (Reuters) - Six Chadbourne & Parke partners, all of whom worked with the firm's longtime client British American Tobacco, said Thursday they planned to join London-based Herbert Smith in September.

The group includes Thomas Riley, who had been the head of Chadbourne's litigation department, and Gregory Loss, who led its products liability group. Five of the partners are based in New York, where they plan to open an office for Herbert Smith.

Chadbourne in a statement said the firm regretted the partners' decision to leave "but understand their business justifications for doing so."

Herbert Smith is one of a handful of firms that British American Tobacco turns to most often for legal work. The Chadbourne group has worked with the company for years and had represented the tobacco giant in a variety of matters, including a $450 million lawsuit by hospitals in Missouri against the tobacco industry that ended in a defense verdict in March 2011.

They also represented British American in the Department of Justice's $280 billion racketeering lawsuit against the tobacco industry in 1999. After 11 years of litigation, the case against British American was dismissed last year.

"We remain committed to a strong products liability litigation practice in the U.S. and internationally," said Andrew Giaccia, Chadbourne's managing partner. "We wish the tobacco team well."

Riley declined comment.

A spokesman for British American Tobacco in a statement said it intended to continue to hire Chadbourne in the future.

Herbert Smith's hiring of the Chadbourne lawyers comes as the firm pushes to expand internationally. Earlier this year it said it would open in New York, and in June it announced it would merge with Australia's Freehills. If completed, the Freehills merger will create a 2,800-lawyer firm called Herbert Smith Freehills with 20 offices globally.

Anthony Dempster, a partner at Herbert Smith spearheading the firm's New York plans, acknowledged the close relationship the incoming Chadbourne team had with British American Tobacco, a mutual client of Herbert Smith's.

But he cautioned against overemphasizing the tobacco work, saying Herbert Smith expected the partners would work on a number of assignments for its network of international clients.

"They are actually commercial litigators with a huge amount of expertise," Dempster said.

Tobacco litigation in the United States has been on the wane since the 1990s, when tobacco companies reached a $200 billion settlement agreement with states attorneys general. The settlement covered Brown & Williamson, a then operating subsidiary of British American.

While personal injury litigation against tobacco companies continues, particularly in Florida, many of the ongoing court fights focus more on regulations over cigarette packaging and advertising.

Dempster said Herbert Smith anticipated more hiring for the New York office, which he expected would have nine partners by the end of the year. The firm is seeking to recruit partners experienced in arbitration and investigations, he said.

Chris Parker, an international arbitration partner already at Herbert Smith, is relocating from London to join the New York office.

Herbert Smith said it grossed £480 million ($746.6 million) in its fiscal year ending April 30, up 3.2 percent. Profits per partner, meanwhile, slipped 5.8 percent to £840,000 ($1.31 million).

Chadbourne by contrast grossed $306 million in 2011, down 0.2 percent, according to The American Lawyer. Profits per partner declined 0.8 percent to $1.32 million.

(Reporting By Nate Raymond)

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