Output in the nation's factories fell by 2.1 percent last month, the fourth consecutive monthly decline and the biggest drop since May 1980, the Federal Reserve Board reported yesterday.

Last month's cutback in industry's production confirmed that the recession has intensified in the final quarter of this year. During November unemployment jumped sharply to 8.4 percent of the work force, according to figures released earlier this month. As firms slow production to compensate for falling demand, there are increasing layoffs and fewer vacant jobs.

The contraction in output was widespread, the Federal Reserve Board said, with "large cutbacks in output of consumer durable goods, construction supplies, business equipment and both durable and nondurable materials."

The auto industry, which has been extremely hard hit by the high interest rates this year, declined further last month as assemblies fell almost 13 percent from an already low level in October.

Housing also has been depressed this year, and the effects have spilled over into industries that make household goods and furniture. There was a drop of more than 5 percent in the production of all home goods in November, reflecting a "deep cut in the production of appliances," the Fed said. Construction supplies fell by 2.1 percent.

There was an overall drop of 2.4 percent in manufacturing output from October to November, with durable goods down 3 percent and nondurables off 1.5 percent, the report said. Durable goods sales are more sensitive than nondurables to recession because they generally are larger-ticket purchases that people or firms can postpone. Within this category there were large declines in the output of basic metals and parts for consumer durable goods and for business equipment.

Industrial production in November was 1.8 percent below the level of a year earlier, the report said.