Employes of The Washington Post represented by the Newspaper Guild yesterday rejected the company's final offer to settle a 14-month contract dispute and voted to set up informational pickets at the newspaper's office.

The company said it had offered the Guild workers a new four-year contract providing average raises of 6.6 percent retroactive to July, 1982, and wage and fringe benefit increases of 6.5 percent this year, 6 percent next year and 5.8 percent the year after.

The fringe benefits offered by The Post included increases of up to 40 percent in pension benefits and a tax deferred savings and investment plan to which the company would contribute up to 2 1/2 percent of an employe's annual salary.

A statement issued by Boisfeuillet Jones Jr., counsel to the paper, said, "The Washington Post, though disappointed by the Guild's rejection of The Post's final offer, expressed hope that the union would reconsider its position and accept the offer." Jones noted that the package offered the Guild was consistent with contracts accepted within the last year by six of seven other Post unions.

Union representatives said the workers turned down the proposed new contract "because they considered it inadequate." Martha Hamilton, co-chairperson of the bargaining committee, said the contract proposal "has pay increases that guarantee we'll lose real earning power over the life of the contract because our pay won't rise as rapidly as the cost of living."

Hamilton said union members will demonstrate outside the Post building on 15th Street NW during the lunch hour this week and will "take other steps aimed at making The Post continue to negotiate rather than give us a take-it-or-leave-it offer."

"Pay is not the only issue, but it's by and large the most important," said Hamilton. She said The Guild is seeking bigger overall wage increases, higher minimum pay scales, cost-of-living protection, job security for workers threatened by automation, a shorter contract, and overtime pay for workers not now entitled to it.

The Newspaper Guild represents about 1,350 full-time and part-time Post reporters, editors, clerks, advertising sales persons, telephone operators, accountants and other white-collar workers. The union's contract with the paper expired in July 1982 and employes have not had a contractual raise since July, 1981.

The company made what it described as its final offer last Friday. Jones said the offer would bring the average annual salary of reporters to $43,500 a year. "We believe that our offer would place The Post among the top newspapers in the country, in terms of actual salaries paid reporters and other employes in the Guild unit."

The union, however, claims the proposal would leave the minimum pay for top classifications in the newsroom and other departments at $616.50 a week, compared with $747.90 sought by The Guild.

What happens next "depends on how the Guild responds," Jones said. "If they don't have anything else to offer, we would have to consider ourselves to be at impasse."

Under federal labor law, a company can formally declare an impasse in labor negotiations and then unilaterally set both wages and working conditions. A union can challenge the company action with the National Labor Relations Board.

Jones would not speculate on whether the company might take that action, but said, "Obviously The Post would like to see the employes soon get an increase."

Hamilton said the possibility of a strike against the newspaper "is not something we took up at this meeting." The contract was rejected in a show-of-hands vote that union officials estimated was about nine to one against the proposal.