Giant condom in Sydney goes global

Christian activists have criticised as disappointing and inappropriate an 18-metre bright pink condom on display in Sydney's CBD.

The Hyde Park Obelisk was turned pink on Friday by NSW health promotion group ACON as part of an HIV prevention campaign but not everyone is a fan.

Wendy Francis of the Australian Christian Lobby said she found the publicity stunt "disappointing" despite it gaining widespread support on social media.

"The caricature of a naked penis with a condom on it is inappropriate for open spaces where children can see it," she told AAP.

With HIV diagnoses in Australia remaining stable at a 20-year high, campaigners said prevention was an important message.

ACON CEO Nicolas Parkhill said he was "thrilled" with the response the condom has generated.

"There's been significant media interest here in Australia and people all over the world are loving the idea as can been seen by the massive engagement on social media," he told AAP.

He said that spreading the message was a "challenge".

"I think people don't see HIV as the risk that it was 30 years (ago)," he said.

He said gay men in particular need to be aware, with 80 per cent of new HIV infections occurring in the gay community.

"That fight is not over," he said.

About 26,800 people are living with HIV in Australia, according to a national report compiled by the University of NSW in July.

It said more than 1200 people were diagnosed with the virus in 2013 with about 14 per cent unaware they even have it.

The "I'm On" safe-sex education campaign is running ahead of World Aids Day on December 1, with the condom set to last a week.