In France the largest political party until 1956 was the communist party. In 1948 the communist/socialist alliance was almost elected to power in Italy, and the communist party was getting over one third of the vote to 1976 (the Italian socialist party with hammer and sickle logo got about 10% of the vote, and Maoist parties got hundreds of thousands of votes). Too much widespread support at the time to ban.

Not in West Germany which reinstated the Nazi ban on the communist party. Not the USA which banned the communist party, criminalized the party and jailed its leaders ( https://en.m.wikipedia.org/wiki/Communist_Control_Act_of_195... ). South Korea, South Africa, Indonesia wtc. all followed the same path.

Dissenting parties were outlawed in western and western aligned countries all over the world, and many of them like Japan, South Korea, France, Italy, Australia etc. became one party led states.

Australia did not outlaw the Labour party, but we can see what happened when the Liberal party interrupted the 1949 to 1983 Cold War rule led by the Liberal party - pressures national and international undermined any ability to rule until a foreign monarch had her footman toss him out.