The government issued a proclamation today banning all public meetings to commemorate the 1976 Soweto uprising in a bid to thwart plans for large-scale black demonstrations to mark the 10th anniversary June 16.

Law and Order Minister Louis le Grange signed the order hours before mixed-race and Asian representatatives began a stalling procedure in Parliament that could prevent two tough new security bills from being passed into law before the anniversary date.

The bills enable the government to assume powers of martial law in designated areas without formally declaring a state of emergency and to increase its already extensive powers of detention without charges.

Le Grange has been trying to rush the bills through Parliament before June 16. He told the dominant white house of the racially segregated three-chamber legislature, which passed the first bill today, that he needed them "very urgently" in the light of "serious circumstances" facing the country.

Helen Suzman, the white antiapartheid legislator whose Progressive Federal Party opposes the bills, suggested tonight that Le Grange may have decided on the ban because his bills were being held up. The minister offered no immediate explanation. The ban is effective from today until June 30.

Suzman and other members of her party predicted that instead of preventing unrest during the anniversary, the ban on meetings would lead to greater confrontation between the police and black activists.

"This is an extremely stupid move," said Tiaan van der Merwe, who led the opposition debate on the first bill, called the Public Safety Amendment Bill. "There is no chance that the blacks are going to heed the ban and allow June 16 to pass without any commemoration, so all it will do is create an extra element of conflict."

Meanwhile, the far rightist Conservative Party criticized the government for creating a constitutional situation in which nonwhite representatives could render it "powerless" by holding up security legislation.

"Who is baas [master] in South Africa if the government cannot proceed with legislation without the consent of the Coloreds [people of mixed race] and Indians?" asked Casper Uys, a Conservative legislator.

June 16, the day on which schoolchildren in Johannesburg's black satellite township of Soweto began a wave of demonstrations in 1976 that eventually resulted in more than 600 young blacks being shot to death by police, has become the most emotive date in the black nationalist calendar.

Black activist organizations and labor unions have decided to make this year's 10th anniversary the high point of their antiapartheid campaign. They called for nationwide commemorative rallies on June 16 itself and a total work stoppage from then until June 18.

While businessmen are worried about the prospect of a general strike at a time of deepening economic recession, some have expressed understanding for the way blacks feel about the anniversary and have said they will not penalize employes who do not come to work.

Two of the most influential firms, the giant Anglo-American Corp. and an industrial conglomerate called Premier Milling Group, have announced that they will treat June 16 and May 1, international workers' day, as public holidays.

President Pieter W. Botha and his ministers have made a series of speeches warning that they intend to crack down more severely than ever on the people they believe are behind the continuing racial strife in the segregated townships.

A week ago le Grange produced the two new bills, which add to an already formidable armory of security legislation.

To become law, a bill must pass through all three houses, but if one votes it down the veto can be overriden by referring the bill to a President's Council of nominated members where the government has a built-in majority.

In light of the nonwhite legislators' stalling maneuver, observers said, the bills probably would not become law until after June 16.