U.K. investor advisory group Pension Investment Research Consultants Wednesday joined the growing opposition to Royal Dutch Shell PLC's (RDSB.LN) decision to award executives a performance bonus despite missing internal targets.

"We recommend shareholders oppose the remuneration report," at Shell's annual general meeting May 19, PIRC said in a statement. The decision of Shell's remuneration board to award the bonuses "undermines [the] consistent long-term approach to performance," PIRC said.

One of Shell's largest shareholders, Standard Life Investments, also criticized the company's remuneration decision Tuesday.

"This is the second year in a row that the remuneration committee has used its discretion to reward the executives for below-average returns to shareholders, which raises serious questions about whose interests they are looking after. We have voted against Shell's Remuneration Report for each of the last three years," said Guy Jubb, head of corporate governance at Standard Life Investments, which is part of asset manager Standard Life PLC (SL.LN), in a statement.

The Association of British Insurers, which advises insurance companies that invest in equities on corporate governance, has issued an "amber" alert on Shell's remuneration plans, and shareholders should consider if the exercise of discretion is appropriate in this case, a spokesman said.

Shell came fourth among its peers in an internal ranking, which under the rules of the long-term incentive scheme should have meant executives received no share bonus. The difference with the third-placed company, Total SA (TOT), was marginal and the remuneration committee looked at a variety of performance measures and results and concluded that the ranking "didn't reflect Shell's underlying strong performance," a Shell spokesman said. Executives were awarded half the shares they would have received in third place.

Company Web site: www.shell.com

-By James Herron, Dow Jones Newswires; +44 (0)20 7842 9317; james.herron@dowjones.com