Sen. David H. Pryor (D-Ark.) accused the Reagan administration yesterday of a "flagrant" abuse of power by mobilizing its nationwide network of Agriculture Department employes to lobby for passage of a farm bill acceptable to the White House.

The lobbying campaign, according to USDA documents obtained by Pryor, includes an order lifting budget restrictions on travel expenditures so that officials can make speeches and address groups in their home states.

The department's campaign packet, distributed to state Agricultural Stabilization and Conservation Service (ASCS) offices around the country, also includes news releases with blank spaces for officials to insert their names following appropriate quotations defending Reagan administration farm policy.

The packet was sent out last month by Everett (Bud) Rank Jr., national director of the ASCS, with instructions to state officials to report back to Washington on news media coverage of the campaign, along with newspaper clippings.

Rank's memo to state ASCS officials alluded to a nationwide conference call by Agriculture Secretary John R. Block, asking their support in promoting administration views on the farm bill. Rank also sent a list of "talking points" to be used in the publicity campaign.

Both the House and Senate Agriculture committees, responding to depressed conditions in the farm economy, have produced farm bills that run counter to the administration's insistence that federal farm program spending be curbed and that farmers be forced toward "market oriented" policies.

In a floor statement yesterday, Pryor told the Senate that he thinks that the administration's publicity campaign on its own behalf "directly violates the separation of the functions of the legislative and executive branches of government."

Pryor said he found it "appalling" that after USDA had restricted the use of travel funds appropriated by Congress, the money would now be available "as long as you're out there preaching the gospel according to John Block."

The Arkansas Democrat, a member of the Senate Agriculture Committee, said he questioned "the priorities of a secretary of agriculture who diverts the already limited manpower and financial resources of his department from the American farmer's immediate needs to efforts to manipulate the farmer to support administration policies."

"The administration on one hand is telling farmers to be frugal, but is taking away travel restrictions for federal employes to sell the John Block farm policy," he added.

Meanwhile yesterday, the administration circulated a long list of objections to the Senate committee's bill. Block's cover letter did not repeat earlier threats of a presidential veto if White House terms are not met.

The House is scheduled to resume voting today on its farm bill, with a showdown expected over a provision by Rep. Berkley W. Bedell (D-Iowa) that would allow farmers to vote on a mandatory-production-control program. The administration has warned that inclusion of that provision would bring a veto.