More law firms and corporate legal departments plan to add staff the first quarter of 2012 than in the fourth quarter of 2011, according to the Robert Half legal hiring index released this week by Robert Half International Inc. (NYSE: RHI).

Thirty-one percent plan to add legal staff in the first quarter of 2012 and 4 percent plan reductions in personnel for a net 27 percent to increase hiring, according to the index’s survey. The net 27 percent increase is up from the net 24 percent increase forecast for the fourth quarter.

Lawyers, paralegals and legal secretaries are the three most in-demand positions.

The Robert Half legal hiring index is based on 200 telephone interviews with lawyers. One hundred of the respondents are employed at firms with 20 or more employees, and 100 are employed at companies with 1,000 or more employees.