Ad spending fell sharply at the end of 2008 and is off to an even worse start this year, a new report shows.

The latest figures from ad tracker TNS show that expenditures plunged 9.2 percent in the fourth quarter from the same period a year ago, compared with a full-year decline of 4.1 percent, to $141.7 billion.

The declines accelerated in the first three months of this year. Although the official numbers haven’t been released, spending is on track to fall between 15 percent and 20 percent in the first quarter, said Jon Swallen, TNS’ head of research.