The union representing Washington-area supermarket workers yesterday rejected a request to pass up the 70-cent-an-hour wage increase scheduled to go into effect Sunday under a union contract negotiated last year.

A poll of union members showed they are 20 to 1 against accepting the wage freeze, said Thomas McNutt, president of Local 400 of the United Food and Commercial Workers Union.

McNutt formally rejected the request for a freeze in a letter to Roger Olsen, vice president for labor relations of Giant Food Inc. and this year's spokesman for the Food Employers Labor Relations Association, which negotiates with the union on behalf of four big chains.

The three-year contract signed last September gives union workers raises of 70 cents an hour each year. Effective Sunday, the hourly pay of checkout clerks will increase from $8.70 to $9.40. Pharmacy workers in the stores earn about $2 an hour less, and meat cutters and some others qualify for higher wages.

Giant, Safeway, Grand Union and Memco had asked their employes to waive this year's raise, citing conditions in the national economy and recent profit problems caused by this summer's supermarket price war.

McNutt said his union is not to blame for the chains' poor profits.

"If they had doubled their profits, I can guarantee they wouldn't have called up and offered to give us more," McNutt said in a telephone interview.

In his letter to Olsen, McNutt noted that, "By their own admission, the losses incurred by Giant and Safeway were of their own doing in an attempt to increase their share of the market.

"We have difficulty in passing the cost of competitive battles on to our members who in these difficult times are faced with the bleak prospect of escalating inflation and a government whose failing economic policies place the heaviest burden in recent years on wage earners," the union official's letter added.

McNutt also disputed the food chains' claim that high wages were making it possible for nonunion chains to move into the market, saying that "almost 90 percent of the area's food dollars are being rung up on cash registers in union stores."