Consumer confidence, which had been depressed for much of 1976, advanced sharply in December to its highest level in nearly a year, according to the latest Conference Board survey of consumer sentiment and buying intentions made public today.

The improvement was tied to both a strengthening of economic fundamentals and potimism about the incoming Carter administration.

The consumer confidence index jumped to 91.2 in December, up 11 points from the previous bi-monthly survey in October.

And the buying plans index rose even more steeply, spuritng 23 points to 122.6 last month as consumers significantly steeped up their plans to purchase automobiles, homes and appliances and to take vacations over the next six months.

A pick-up in consumer spending was detected during the last two months of 1976, with Christmas retail sales coming in stronger than expected. And the results of the current Conference Board survey should bolster those economists who see a more confident consumer fueling a new acceleration in the U.S. economy's growth rate after the mid-1976 slowdown.

"The sharp turnaround in consumer sentiment can be attributed to both economic and psychological factors," observed Fabian Linden, director of consumer research for the Conference Board, a non-profit independent business research organization.

"It appears to reflect natural hopefulness about a new administration in Washington, the recent quieting of inflation, and sturdy improvment in real disposable income," he added.

The improvement was across-the-board in the latest survy, which is conducted every two months for the Conference Board by National Family Opinion, Inc., and polls more than 10,000 U.S. households.

About 25 per cent of those polled believe business conditions will improve over the next six months, compared with only 20 per cent in October. On the employment front, only 11 per cent of those surveyed look for a drop in jobs over the next six months, down from about 17 per cent in October. And some 30 per cent expect their incomes to rise during the first half of 1977, up from 27 per cent in the previous survey.

Linden noted, however, that consumers retain some caution about present business conditions, and despite the decrease in concern about the job outlook, continue to be worried about the U.S. employment situation. About 38 per cent of those surveyed complained that jobs are "hard to get," he said, down only slightly from the October figure of 40 per cent.

Perhaps the most dramatic part of the new survey is the surge in buying plans.

Plans to buy automobiles, both new and used, over the next six months rose to 10 per cent in December from 7.3 per cent in October. And car-buying plans are now only slightly below the peak levels of last February when car slaes were undergoing a strong recovery.

Similarly, home-buying plans rose strongly, with 4.2 per cent of those surevyed, with 4.2 per cent of those surveyed saying they plan to buy a home in the next six months, up from 3.2 per cent in October. The home buying series of the index is now at its highest level since 1973. And of those polled, 31.4 per cent said they intend to buy a major appliance some time during the first half of 1977, up from 28.9 per cent in October.

The Conference Board consumer confidence index stood at 93.3 last February, dropped to 82.2 in April, rose again to 86.7 in June, stayed steady until October when it declined to 80.2, and then registered the brisk climb in the latest survey in Decemeber to reach 91.2