A group of Florida vegetable growers yesterday appealed a Commerce Department decision clearing Mexican vegetable growers of charges that they have been selling winter tomatoes and other vegetables in the United States for less than the cost of production.

The Florida group said in its 20-page petition filed in U.S. Customs Court in New York that the Commerce decision last month wasn't made in accordance with antidumping laws and that it was done "to avoid the adverse political and foreign-policy consequences of a determination that fresh winter vegetables from Mexico are being dumped in this country . . ."

A decision favoring the Florida vegetable growers might have led to special import duties being levied against the Mexicans that could have pushed up the prices of those vegetables in the supermarkets and hurt the administration's recent anti-inflation efforts. Commerce officials have denied the charge that their decision was politically motivated.

Commerce found that "there was no dumping on the ground that these Mexican vegetables are not sold and are not likely to be sold in the U.S. at less than their fair value." Fair value was determined by comparing the prices at which those or similar vegetables from Mexico were sold in Canada and the United States, betweenNovember 1977 and May 1978.

Canada was used for comparison rather than Mexico, as is usually done, because not enough of the vegetables were sold on the Mexican market, Commerce officials said.

Commerce found that prices in the two countries were "essentially similar" and any differences in prices could be attributed to factors relating to characteristics of the products and market conditions.

"The record contains ample evidence that the price variations observed reflect real differences in the quality and ripeness and supply-and-demand factors at the time of day of sale," Commerce official Stanley J. Marcuss said when the decision was rendered. "These are the kinds of factors for which price adjustments are normally made under the dumping law."

The lawsuit filed yesterday, however, said that the Commerce Department hadn't applied antidumping law appropriately.

The lawsuit said that the decision was based on an analysis of only 34 producers out of about 2,000 Mexican growers and that producers used in the study accounted for less than 15 percent of the winter vegetable imports.

The lawsuit also challenged the Commerce Department's use of Canada as a comparison rather than Mexico and claimed that the decision "is not supported by substantial evidence" and is "based entirely on analysis of such a seriously deficient sample of producers of" the vegetables.

The vegetables involved are tomatoes, cucumbers, eggplant, peppers and squash products that constitute one-half of winter vegetables consumed by Americans, Commerce officials said.