A key measure of business activity strengthened again in December, a lender group told Reuters on Tuesday, as companies borrowed more money to invest in their operations and did a better job of staying current on their existing loans.

The Equipment Leasing and Finance Association said business originated $9 billion in loans, leases and lines of credit in December to invest in everything from tool-and-die machines and delivery trucks to office furniture and computer hardware and software.

That was double the $4.5 billion they borrowed to invest in capital equipment in November and up from the $7.1 billion they financed during the same month last year.

The group, which represents the lenders who finance half the capital investment in the United States each year, said 2.71 percent of borrowers were delinquent 30 days or more on their financings in December. That was down from 3.19 percent in November and 4.3 percent last year and the best showing in two years.

ELFA said lenders considered 1.4 percent of the loans in their portfolios as losses unlikely ever to be repaid last month. That was unchanged from November but down from 2.08 percent last year.

The group said that lenders approved 75.3 percent of capital spending credit applications they received in December, up from 72 percent in November and 68 percent a year before. December capital spending approvals were at the highest level since the start of the recession.

While December is historically a strong month as equipment finance companies complete end-of-year transactions, we continue to be encouraged by the strength and trajectory of these trend lines in business activity, ELFA President William Sutton said.

Construction and trucking sectors, however, continued to underperform in December.

ELFA provided its monthly report to Reuters a day ahead of its official release.

The group's members include Bank of America Corp, Canon Inc affiliate Canon Financial Services, Caterpillar Inc's Caterpillar Financial Services Corp, CIT Group Inc, Dell Inc's Dell Financial Services, Deere & Co's John Deere Credit Corp, Siemens AG's Siemens Financial Services and Verizon Communications Inc's Verizon Capital Corp affiliate, among others.

(Reporting by James B. Kelleher, editing by Gerald E. McCormick)

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