Leah Cooper left her job as managing lawyer for the giant mining company Rio Tinto in February to become director of legal outsourcing for CPA Global, a contract legal services company with offices in Europe, the United States and India. Before hiring Ms. Cooper, CPA Global added lawyers from Bank of America and Alliance & Leicester, a British bank. The company has a total of about 1,500 employees, and Ms. Cooper said she planned to hire hundreds in India in the next 12 months.

At Rio Tinto, Ms. Cooper said, she became a champion of the idea of moving work like document review to a legal outsourcing company “because it works really well.”

“It really is the future of legal services,” said Ms. Cooper, an American based in London who travels regularly to India and has spoken widely in promoting outsourcing. Still, she acknowledges hostility toward the practice. “When I was doing public speaking, people used to joke that I had better check under my car” for something planted by a junior associate angered by her views, she said.

Many legal outsourcing firms have offices around the world to interact with clients, but keep the majority of their employees in India; some also have a stable of lawyers in the Philippines. Thanks to India’s low wages and costs and a big pool of young, English-speaking lawyers, outsourcing firms charge from one-tenth to one-third what a Western law firm bills an hour.

Employees at legal outsourcing companies in India are not allowed by Indian law to give legal advice to clients in the West, no matter their qualifications. Instead, legal outsourcing companies perform a lot of the functions that a junior lawyer might do in a American law firm.

Even global law firms like Clifford Chance, which is based in London, are embracing the concept.

“I think the toothpaste is out of the tube,” said Mark Ford, director of the firm’s Knowledge Center, an office south of New Delhi with 30 Indian law school graduates who serve Clifford Chance’s global offices. Mr. Ford lived in India for six months to set up the center, and now manages it from London.