U.S. investment ratings agency Moody's says activist shareholders are stepping up the pressure on many of the U.S. companies it rates, often with negative effects on their credit ratings.

At least five new campaigns have been launched this year, the agency notes in its report Shareholder Activism: Impact on North American Corporate Sectors. According to Moody's, hedge funds or investment advisors pursued 220 targets in 2013, up from 209 in 2012 and 179 in 2011.

The agency said it classifies a stockholder as an activist when demands are made public, typically in a 13-D filing or public letter or through a proxy contest or both. Along with healthcare, it said the technology sector continues to experience the most shareholder activism, accounting for a quarter of all 2013 activist campaigns at both rated and non-rated companies.

Cash-rich companies with minimal debt are the most frequently targeted, Moody says, adding that the activists have prompted their management to sell underperforming businesses and implement cost-reduction schemes as well as increasing dividend payments and share buybacks.

This, it said, has resulted in reduced financial flexibility, lower cash balances and reduced ability to spend on large capital projects or debt-financed acquisitions. Up to now, however, their creditworthiness has not been impaired enough to warrant a ratings downgrade, the agency concludes.

Among chemical players Moody's points to as targets are DuPont, Dow, Monsanto, LyondellBasell, Celanese, Rockwood Holdings, Albemarle and Huntsman. Dow recently made headlines when it was targeted by the hedge fund Third Point, which - after disclosing that it had acquired a sizeable stake in the company - urged management to hire outside advisers to review the potential benefits of spinning off its petrochemicals activities.

Earlier, DuPont had announced plans to spin off its $7 billion Performance Chemicals division, including the titanium dioxide and the chemicals and fluoroproducts businesses, to its shareholders over the next 18 month, a move market watchers attributed to pressure from activist shareholders.

The same investor strategy is also said to have prompted Rockwood's decision to exit the titanium dioxide business. This is planned to be picked up by Huntsman, depending in part on the outcome of a deep probe by EU authorities who have competition concerns.