LABOR frontbencher Penny Wong has taken another swipe at the Coalition over its same-sex marriage plebiscite plan, saying Prime Minister Malcolm Turnbull knows that the vote has been designed by people “who are opposed to marriage equality”.

Speaking on ABC’s Lateline on Monday night, Senator Wong said Mr Turnbull has been “forced into a plebiscite position” by Deputy PM Barnaby Joyce and the conservatives in the Liberal Party.

“It amounts to a sabotage of the plebiscite,” the senior Labor figure told Lateline host Emma Alberici. “That is what the conservatives want. I mean, the irony is, here we have got Malcolm Turnbull telling us, ‘We want a people’s vote.’ He knows. He knows that this vote has been designed by [Senators] Cory Bernardi, Eric Abetz and many others who are opposed to marriage equality. They only want a plebiscite because they think they can make it work to defeat equality.”

Despite Mr Turnbull insisting last week that same-sex legislation will “sail through” parliament if a plebiscite is successful, Senator Wong argued that in the nine months since he has been Prime Minister, Australians are yet to have a bill, any idea of how much it will cost or “any information about how he would fund the case.”

Senator Abetz is yet to say whether he would support a peoples’ vote to legalise same-sex marriage. “There are too many hypotheticals at this stage for me to lock myself in,” he told AAP last week. “To ask people to determine what they might do at the end of the plebiscite is highly hypothetical.”

Senator Wong — who is in a long-term same-sex relationship and has two young daughters — implored voters: “If you want marriage equality, vote Labor on Saturday.”

Senator Wong’s comments come one week after her powerful speech delivered at the annual Lionel Murphy Memorial Lecture. Speaking to a packed Australian National University audience, she argued that heterosexual politicians were unable to understand the hatred lesbian, gay, bisexual, transgender and intersex (LGBTI) Australians would endure if a national vote was held on the issue.

“A plebiscite designed to deny me and many other Australians a marriage certificate will instead license hate speech to those who need little encouragement,” Senator Wong said.

“Mr Turnbull, and many commentators on this subject, don’t understand that for gay and lesbian Australians, hate speech is not abstract. It’s real. It’s part of our everyday life.”

Meanwhile, Tony Abbott’s former chief-of-staff Peta Credlin predicted a “schism” in the Coalition over the gay-marriage vote.

During an appearance on Sky News, Credlin pointed the finger at Mr Turnbull and senior government officials for not having “any plan B” is the plebiscite fails to pass the Parliament and even suggested it could threaten his position as prime minister.

“How does it play out? Because no one on the Government side has been very comprehensive and straight about the plebiscite,” Credlin said.

“I think it will be a very big schism inside the Liberal Party going back to territory of 2009,” she predicted.

“Malcolm knows that very well because that’s where he lost his leadership. I think it will also cause enormous stresses within the Coalition.”

On ABC’s Q&A, controversial broadcaster Alan Jones again voiced his opposition to the proposed same-sex marriage plebiscite.

“Let me nail my colours to the mast — I’m certainly opposed to a plebiscite on this issue,” Jones said. “And I think that when Bill Shorten made his observations about that and he argued a plebiscite was homophobic, that wasn’t what he was saying. He was trying to avoid the kind of exchanges that would occur if a plebiscite took place.

“Turnbull was in favour of a vote of the Parliament and he represented that view to me when he was the Minister for whatever it was, NBN or something. Before he became PM. And I think it would be very unfortunate if we went down a track where we have spent a whole heap of money and people throwing insults at each other,” the radio commentator said.

When asked why Australians should be wary of a plebiscite, Jones responded: “Parliament. We select 150 in the House of Representatives to represent those 22 million people on critical issues such as this.

“I think we should do what Malcolm Turnbull originally said we should do, let the Parliament decide.”

The coalition intends to hold a plebiscite by the end of the year if it wins on July 2.