"Investing in people and communities will produce dividends for credit unions in many respects, but the higher interest rate environment of late 2013 and the first quarter of 2014 slowed mortgage originations," NCUA Board Chairman Debbie Matz said. "To protect the Share Insurance Fund, the NCUA continues to closely monitor the risks posed by rising interest rates, long-term investments and fixed-rate mortgages."

According to the report, outstanding loan balances were up 8.8% in the first quarter of 2014, from the same period last year. New auto loans increased 13.9% to $73.5 billion and used auto loans grew 11.3% to $130.1 billion. Net member business loan balances also increased 11.1% to $47.3 billion.

Credit union membership grew by 831,635 to reach a record high of 97.1 million, while credit union assets increased 3.4% to $1.1 trillion, from $1.06 trillion in 2013. Net worth grew 1.8% to $116.6 billion, from $114.5 billion in the first quarter of 2013.

The agency said federally insured credit unions remain well capitalized. The amount of well-capitalized credit unions increased 1 percentage point in the first quarter of 2014 compared to same period last year. Overall, 96% of credit unions reported a net worth at or above the existing requirement of 7%.

Reacting to the latest data, NAFCU said the NCUA should withdraw the proposed risk-based capital rule.

"The first-quarter data shows credit unions continue to meet the high standards of value and exceptional member service that people want in their financial institutions," said Carrie Hunt, NAFCU SVP of government affairs and general counsel. "Moreover, credit unions continue to be a vital source of credit in helping small businesses expand and promote job growth on Main Street. We want to see these trends continue and believe a key step toward ensuring a sustained recovery is for NCUA to withdraw its proposed risk-based capital rule."