The first major advert from the “no” campaign in Australia’s same-sex marriage plebiscite, which could lead to its legalisation, aired on Tuesday night and has been accused of “scaremongering”.

It features three mothers linking same-sex marriage to things like Australia’s anti-bullying Safe Schools programme – which promotes inclusivity – and has been described by opposition leader Bill Shorten as “offensive and hurtful”.

The Coalition for Marriage, the main body behind the no campaign, also uploaded the ad online where it has received an overwhelmingly negative response on YouTube and other social media.

The first mother, Cella White, said that “the school told my son he could wear a dress next year if he felt like it” – a claim the school’s principal denied to The Australian.

The third mother said that “kids in year seven are being asked to role play being in a same-sex relationship”, while the advert’s tagline “you can say no” echoes the Australian Conservatives’ slogan “it’s OK to say no”.

Labour leader Mr Shorten told Fairfax Media: “This is not freedom of speech. This is freedom to hurt. I just want to tell LGBTI families that they are not on their own. Most people know this is total rubbish.”

Tiernan Brady, executive director of the Equality Campaign, said: “The people behind this ad know that the Australian people are for allowing all Australians the right to marry, so they have resorted to misleading people, to pretend this is about something else.”

As much as the no lobby want you to believe otherwise, a vote for #marriageequality has zip to do with Safe Schools @TonyAbbottMHR #auspol — Christine Forster (@resourcefultype) August 29, 2017

Just saw an ad for the 'You can say No' campaign. The coalition should be ashamed of themselves for scare mongering in schools. — Deborah Seabrook0888 (@seabrook0888) August 29, 2017

Just saw the first vote no on same sex marriage ad on tv.. some of the stuff said was ridiculous. — Mel (@Its_Me_Mel_) August 29, 2017

Sophie York, of the Coalition for Marriage, defended the ad in a statement.

“Millions of Australians are now concerned about the consequences of changing the Marriage Act,” she said.

“Australian parents have a right to know how a change in the marriage law will affect what their kids are taught at school. The education departments won’t tell them. Those lobbying for change won’t tell them.”

Australia is one of the last English-speaking Western countries where same-sex marriage is illegal, despite polls showing more than 60% of the population believe it should be allowed.

The country will undertake a non-binding, non-compulsory postal vote beginning on September 19, where if there’s a “yes” win a conscience vote will take place in the Australian parliament. If it is a result for no, there will be no vote in the Australian parliament.

PA Media