The light show planned for the Opera House to advertise the Everest horse race has been moved forward an hour to avoid protests.

The controversial promotion on the sails will now begin at 7:00pm, not 8:00pm.

A statement from Defending the Opera House said the racing industry had decided to start the event earlier.

All betting for the Everest horse race has been suspended, with Racing NSW stewards citing "security risks" amid a fiery debate about the use of the Sydney Opera House to promote the event.

Key points: The barrier draw was to be conducted live with results projected onto the Opera House

The barrier draw was to be conducted live with results projected onto the Opera House It has now been done in secret to "circumvent any security risks"

It has now been done in secret to "circumvent any security risks" Betting was suspended at midday to avoid any perceived integrity risk

Racing NSW also revealed the barrier draw had been conducted in confidence and the result would be kept secret this evening.

"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 original plan was to conduct a live barrier draw and project the result onto the Opera House sails.

Alan Jones called for Opera House chief executive Louise Herron to be sacked. ( AAP: Tracey Nearmy/Tracey Trompf )

Opera House chief executive Louise Herron opposed that plan last week, saying it would breach guidelines that limit what can be projected onto the building.

The NSW Government overrode that position after broadcaster Alan Jones clashed with Ms Herron in a heated on-air discussion about the merits of the race and its value to the economy.

Mr Jones today apologised for the comments he made during the interview, saying he regretted the words used having heard their impact.

Racing NSW said betting had been suspended from midday "to avoid any perceived integrity risk".

Premier Gladys Berejiklian has defended the decision to allow the promotion, saying it would be done "in good taste" and the approved proposal was a toned down version of what was originally planned.

Supporters of the event have drawn comparisons to the Opera House being used to advertise rugby and cricket events.

However, there has also been a fierce backlash against the idea, including a "passive" protest planned for Tuesday night to disrupt it.

Protestors have been brainstorming how to detract from the images and while many say powerful torches will be an effective statement, some have suggested the use of balloons or sheets to cover the main projector.

An online petition against the event was delivered to State Parliament this morning. It had attracted more than 270,000 signatures on Tuesday afternoon.

The controversy has unfolded during the NSW Government's "Responsible Gambling Awareness Week", which invites residents to check in on their friends and family members about their gambling habits.

A mock-up of the projected barrier draw that will appear on the Sydney Opera House tonight. ( Supplied: Racing NSW )

The race is to be held at Sydney's Royal Randwick, billed as the city's answer to the Melbourne Cup.

It has been promoted as the world's richest race on turf, with $13 million in prize money, and will take place on October 13.

Federal politicians have weighed in on the stoush, including Prime Minister Scott Morrison who believes the promotion of the event is a "no-brainer".

"These events generate massive economic opportunities for the state, for the city," Mr Morrison said.

Opposition Leader Bill Shorten said communities draw a line at "describing national heritage as a billboard".