The Climate Change Act passed last year set 43 per cent as our destination, an important symbol. How we actually get there - the engine to drive our transition - is called the safeguard mechanism. But there is a very real risk that without serious amendments to protect climate integrity, the safeguard mechanism will be a house of cards built on phantom offsets.

The safeguard mechanism is supposed to tackle ballooning emissions from Australia's biggest polluting industries. It is a highly complex and technocratic jumble; a leftover policy from the former Coalition government that is likely to cause headaches when it's debated in Parliament in March.

Complexity can hide a multitude of sins, and as the world's third largest exporter of fossil fuels, the rest of the planet cannot afford for Australia to get this wrong.

One of the biggest problems with the safeguard mechanism is it does not require big polluters to reduce their emissions in the absolute sense; instead it effectively gives them a get-out-of-jail-free card by allowing them to buy unlimited carbon offsets as an alternative to reducing their emissions. At a very basic level, the idea is that if someone doesn't cut down a tree on their property, then Woodside is free to keep expanding and extracting gas. Someone else has nominally reduced their emissions, therefore Woodside doesn't have to.

Before we get into some of the problems with offsets themselves, let's get one thing perfectly clear: offsets don't reduce emissions. At all. It's great to avoid cutting down a tree.

But if you avoid cutting down that tree so that Woodside can continue polluting, nothing has changed. The very best you can hope for is that the status quo has been maintained.

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Australia simply cannot offset its way to 43 per cent by 2030. It's impossible. The goal is decarbonisation in line with the science, not creative accounting. Polluting industries and companies that can do so must directly reduce their emissions for Australia to legitimately meet its targets. Yet, the more offsets are bought, the less decarbonisation happens.

Every dollar spent on an offset is a dollar that cannot be spent on technology that will permanently displace the fossil fuels causing global warming. It's no coincidence clean energy investment in Australia has seen a major drop when energy retailers can just buy cheap offsets and tell their customers they're carbon neutral. Why go through the inconvenience of changing your business model if you can just buy some offsets?

Carbon offsets are supposed to be a last resort, reserved only for companies and industries for whom it will be most difficult to reduce emissions.

However, for too many companies offsets seem to be the first port of call and the government is actively endorsing this approach with its voluntary carbon neutral certification Climate Active.

The safeguard mechanism is dominated by the coal, oil and gas industries who plan to increase production, which means increased emissions. Under the government's proposed policy, this can happen as long as they buy enough carbon offsets to theoretically neutralise their emissions. In other words, coal, oil and gas can and likely will expand under the government's key climate policy as currently proposed.

Which leads us to a much more serious problem. What happens if those carbon offsets are junk? That is, what happens if a farmer does not cut down a tree they were never going to cut down in the first place, but Woodside or Santos is still allowed to keep polluting?

The result is an increase in emissions. And there is a very real risk that this will happen under the government's proposed safeguard mechanism.

Seemingly every week there is a media story about junk carbon offsets. Just this week, at least two separate peer-reviewed studies concluded more than 90 per cent of rainforest carbon offsets by one of the world's biggest providers are basically worthless. Analysis by Australian academics and independent experts has also found manifest flaws with Australia's carbon credits, suggesting around 75 per cent of them are of low integrity. Again, when a big emitter buys an offset that is junk, emissions increase. By allowing unlimited offsets under the safeguard mechanism, the government is effectively saying it's willing to let that happen.

The day before the government announced its safeguard mechanism would allow industry to offset as an alternative to legitimate reductions, a review was released which, coincidentally, gave Australia's carbon offsets a clean bill of health. Funnily enough, the findings of the Academy of Science report commissioned by the offsets review panel - which confirmed the problems raised by experts - just didn't make it to the final report. The whole review raised more questions than it answered.

But if the whole point of the carbon offset review was to make the issue of junk carbon offsets go away - it hasn't worked. Instead it's put a spotlight on them just weeks before the Parliament is set to consider whether the safeguard mechanism legislation should have unlimited offsets.

MPs who care about climate change and climate integrity would be wise to consider what role, if any, is appropriate for offsets in the safeguard mechanism legislation.

Where is the incentive or the requirement for polluters to actually reduce their emissions if they have access to unlimited, dodgy offsets? The simple fact is the more offsets we use, the less we actually decarbonise the economy.

The safeguard mechanism, if it passes, is due to come into effect on July 1, only 76 months away from 2030. The clock is ticking and the stakes are high. Australia is already facing the impacts of climate change with all the extreme, "once-in-a-century" weather events that seem to happen every other year. The former Coalition government already wasted the last decade. Australia simply cannot afford to legislate an ineffective emissions reduction policy, with fossil fuel expansion and unlimited offsets at its heart.