Tower group has reported a net income available to common shareholders of $33.7m, or $0.78 diluted earnings per share for the third quarter of 2010, compared to $29.9m or $0.74 per diluted share, for the same quarter of 2009.

Reported total revenue of $423m for the third quarter of 2010, compared to $256m in the same quarter last year.

The revenue growth was primarily due to increased net premiums earned and net investment income resulting from the acquisitions of the OBPL business in the third quarter of 2010 and of SUA and the renewal rights to the AequiCap workers’ compensation business in the fourth quarter of 2009.

Gross premiums written for the third quarter of 2010 was $$447m, compared to $282m in the same quarter last year.

Operating income was $33m for the third quarter of 2010, compared to $30m corresponding quarter of 2009.

Tower Group president and CEO Michael Lee said, during the third quarter, the company has successfully closed on the acquisition of the OBPL business and significantly increased premium volume and fee income.

“As a result, our annualized operating return on shareholders’ equity improved to 12.7% in the third quarter, as compared to 8.7% for the first six months of 2010. We also saw a significant increase in our book value, driven by an increase in the value of our investment portfolio as well as our quarterly earnings,” Lee said.