Two of New York's biggest law firms, Dewey Ballantine and LeBoeuf Lamb Greene & MacRae, have agreed to merge in the city’s largest law firm tie-up to date.

The combination, which will create a 1,300-lawyer firm with revenues approaching $1 billion, comes eight months after Dewey Ballantine’s proposed merger with San Francisco-based Orrick, Hetherington and Sutcliffe collapsed.

The new firm, to be known as Dewey & LeBoeuf, will be run by LeBoeuf chairman Steven Davis. Each firm will have equal representation on a combined management committee, the two firms said in a joint statement.

Dewey & LeBoeuf, which will have operations in 12 countries, will become one of the largest law firms in New York, where both are based and have their largest offices.

The combined earnings of the two firms would catapult the new entity into the top 20 firms in the world by revenue.

After agreeing the earlier deal with Orrick, Morton Pierce, chairman of Dewey, highlighted the combined firms' international reach, suggesting Dewey was particularly attracted to Orrick’s strength in Asia.

But Mr Pierce told the New York Law Journal that it had become “clear that outside New York wasn't the most important [area], it was inside New York".

Dewey & LeBoeuf said its 170-strong team of lawyers in London would make it the fifth-largest US firm there by head count.

The merger, which has been agreed in principle but is subject to partner approval, is expected to be finalised in October.

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