Polish authorities today denied permission to Lech Walesa, leader of the banned Solidarity union, to address a workers' rally outside Gdansk's Lenin Shipyard on Wednesday, the third anniversary of the formation of the union.

Government spokesman Jerzy Urban also said at a press conference that security forces had made sufficient preparations to counter possible demonstrations. A large contingent of riot police were camped on the outskirts of this northern port city tonight.

To mark the anniversary of the signing of the 1980 worker-state agreements that opened the way for Solidarity, the union's underground leadership has called for a boycott of official newspapers and of local public transport during the afternoon rush hour, which could lead to crowds of workers walking together through the streets.

In Warsaw, Krakow and elsewhere in Poland, leaflets have been circulating outlining plans for marches. Last year on Aug. 31 security forces broke up demonstrations in all major cities, and five persons were killed.

Walesa had appealed to Gdansk officials for permission to lay flowers at 2:30 p.m. at the monument outside the shipyard, a memorial erected by Solidarity to workers killed in 1970 in clashes with police. But Urban reported that Gdansk authorities turned down the request out of concern that Walesa's actions could lead to a demonstration.

Gdansk officials said individuals would be permitted to place flowers at the shipyard monument between 4 and 4:30 p.m, and Walesa said he would lay his wreath during that time.