BOSTON, April 28 (Reuters) - Standard & Poor's lowered its ratings on Fidelity Investments parent FMR LLC [FMRCO.UL], citing a decline in profitability, and said its outlook is negative.

The New York rating service said on Tuesday it lowered FMR's counterparty long-term credit rating to A-plus, its fifth-highest rating, from AA-minus, its fourth highest. The short-term rating was cut to A-1 from A-1-plus.

Standard & Poor's said in a press release its action on the family-controlled company "results from a decline in profitability" that could make it harder for FMR to service its debts.

FMR's assets under management fell 22 percent last year to $1.25 trillion, mainly due to market depreciation, the service noted. It also said one-year performance in many of the company's mutual funds "has been subpar, which in our opinion suggests that a near-term turnaround in AUM (assets under management) is not likely."

Fidelity spokeswoman Anne Crowley said in response: "We are positioned exceptionally well. We have unique and diverse business lines, a strong brand and reputation, and a willingness to invest in the future."

Crowley said further than the company's overall liquidity improved in 2008, and its capital "remained strong." (Reporting by Ross Kerber, editing by Leslie Gevirtz)