Slogans like "Pope Go Homo" and "The Pope Is Wrong - Put a Condom On" will be splashed across protesters' T-shirts during next week's World Youth Day (WYD).

Up to 500,000 people are expected to attend WYD events, including more than 100,000 international visitors.

The event will also mark Pope Benedict XVI's first visit to Australia, with the pontiff expected to arrive in Sydney on Sunday.

The NoToPope Coalition held an "annoying fashion parade" outside NSW parliament on Wednesday to unveil the shirts they will wear during a Sydney rally on July 19.

The group fears police will ban them from wearing the shirts, after NSW Police were given powers to arrest anyone they believe is causing annoyance or inconvenience to WYD pilgrims.