Most RIAs offering retirement plan advice are not embracing the retirement plan work and are missing an opportunity for business growth, according to a Fidelity Institutional Wealth Services study released Thursday.

Ninety-one percent of advisors who offer retirement plans are merely “accommodating” the business as part of their other wealth management services, rather than pursuing retirement plan work and developing an expertise in it, says Fidelity.

Those who have pursued retirement plan work and become specialists in it have increased their retirement plan business by 50 percent or more in the past five years, according to the report, the 2013 “Fidelity Retirement Advisor Research Study.” These high-performing advisors are more likely to dedicate time to retirement plans than other advisors: 55 percent of their time is spent on retirement planning versus 41 percent for other advisors.

They also are more likely to direct marketing activities to generating new retirement plan business: 39 percent versus 19 percent of other advisors.

Advising on retirement plans is a huge opportunity for advisors, according to Fidelity. Eighty-four percent of plan sponsors relied on advisors in 2013, an increase of 9 percentage points from the year before.

Fidelity has created a program, Retirement Plan Growth Strategies, to help advisors determine whether they want to pursue retirement plan business and then shows them how to go about it if they do.

“Advisors who expect to only accommodate [retirement] plans will not be able to compete with those who are dedicating real time and resources to it,” says Meg Kelleher, executive vice president and head of the Retirement Advisors and Recordkeepers segment of Fidelity Institutional Wealth Services.