Betting for the controversial Everest horse race has been suspended amid "security risks" ahead of the planned projection of the barrier draw onto the Sydney Opera House on Tuesday night.

Racing NSW stewards said the draw had already been conducted, but would remain secret until the projection is held.

"Racing NSW has made the decision to conduct the draw prior to the event to circumvent any security risks that may exist," the organisation said in a statement.

"Racing NSW stewards shall advise all wagering operators this evening when they may recommence betting on the event."

The plan was for the barrier draw to be held live on Tuesday night and projected onto the sails of the iconic building. Betting was suspended at midday.

Earlier, broadcaster Alan Jones said he now regrets calling for the sacking of the Opera House's chief executive Louise Herron, as opposition to the promotion of the horse race continues to build.

The 2GB talkback host has mounted a strenuous pro-racing campaign and on Friday called for Ms Herron to be sacked over her opposition to projecting an advertisement for the Everest race onto the iconic building.

But on Tuesday morning, Jones backed down.

“I used some words in these programs about the Everest, and the Opera House, and Louise, which in hindsight I now most regret hearing, having heard the impact they’ve clearly had on some people,” he said on air.

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“In relation to Louise [Herron], I was tough regarding an issue I and others felt is very important.”

More than 265,000 people have signed a petition calling on the NSW government to reverse its decision to allow the advertisement.

Petition organiser and Sydney father Mike Woodcock hopes Premier Gladys Berejiklian will accept the petition he started on Friday, after the coalition overturned a decision by Opera House management to reject the plan.

Public outrage over the decision to promote the $13 million Racing NSW race, dubbed The Everest, mounted over the weekend and into this week with some calling it an "assault" on the World Heritage listed Australian icon.

READ MORE Opera House promotion could be illegal: National Trust NSW

Mr Woodcock, whose petition on Tuesday morning topped 230,000 signatures, said it would be "awesome" if Ms Berejiklian reversed her decision made in the wake of Jones' vigorous pro-race campaign.

"On Friday we saw her accept a single phone call from one person that, you know, has a lot of sway in Sydney, apparently," he told Nine Network.

"It would be great if she also accepted the views of 232,000 other people that are on the other side of this."

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His Change.org petition, which the website says is its "fastest growing petition" in recent memory, will be delivered to the NSW Parliament on Tuesday morning.

On Tuesday night, the barrier draw for The Everest is due to be projected on the shells of the Opera House from 8pm, alongside a planned protest on the foreshore.

Protest organiser Rachel Evans says there's "a lot of anger on the streets" about the promotion which she's described as an "assault on the Opera House".

Nearly 3000 people are expected to attend and plan to disrupt the Everest projection with torches and mobile phone lights.

Everest organiser Racing NSW claims its received death threats in the wake of furore. NSW police said on Monday they weren't aware of any reported threats.

Meanwhile, National Trust NSW conservation director Graham Quint says projecting commercial material onto the Opera House contravenes state laws.

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The Racing NSW promotion had been referred to the World Heritage body UNESCO, he added.

The Opera House conservation management plan states "the Sydney Opera House exterior, particularly the shells ... should not be regarded as a giant billboard or commercial/advertising opportunity".

Ms Berejiklian on Friday intervened to allow the advertising after Jones publicly berated Opera House chief executive Louise Herron for standing against plan, saying she should lose her job.

The premier on Monday stood by her decision saying she was "incredibly comfortable" with it, despite widespread perceptions she'd caved in to Jones' demands.

Meanwhile, a NSW Independent MP has said he wants to change state laws governing the Sydney Opera House to remove the power of the government to override management decisions.

Member for Sydney Alex Greenwich said on Tuesday he would move a motion in parliament to amend the Sydney Opera House Trust Act to "stop the culture of a minister picking up the phone on behalf of his mates in the racing industry and telling the Opera House what to do".

"Sydney is not Las Vegas, and out cultural icons should not be used to help the racing industry make a profit from problem gambling," Mr Greenwich told reporters in Sydney.