By Al Yoon

NEW YORK, June 24 (Reuters) - Freddie Mac, the second- largest provider of funding for U.S. home mortgages, has more than tripled its review of individual loans from pools it buys to improve the quality of its holdings, an executive said on Tuesday.

Lax underwriting standards during the housing boom and resulting delinquencies have prompted Freddie Mac and other big investors to boost their reviews.

Freddie Mac (FRE.N: Quote, Profile, Research) has more than tripled its "due diligence" on loans to about half the pools it purchases from lenders from about 15 percent two years ago, Ronald Feigles, a director of conduit risk assessment at Freddie Mac, told Reuters after a panel hosted by the Securities Industry and Financial Markets Association, or SIFMA, in New York.

Due diligence firms give opinions on a set of loans taken from pools. They have existed for decades but were less influential during the housing boom when lenders relaxed underwriting standards to raise volume and stay competitive, said Maureen Palmer, a managing director of The Capital Group, a due diligence service in Greensboro, North Carolina.

"Our sample sizes have done nothing but grow," Feigles said on the panel.

Freddie Mac also oversees the work of due diligence firms, ratherthan accept information outright, he said.

LOSS PREVENTION

Rick Sorkin, a vice president of structured transactions at Fannie Mae (FNM.N: Quote, Profile, Research), the largest government-sponsored enterprise, or GSE, said during a later SIFMA panel discussion that he sees due diligence sample sizes growing.