In a masterclass of corporate irony, Woolworths announced a three-month "Price Freeze" on 300 family staples starting 1 May, promising to help customers grappling with inflation. But pricing data compiled by comparison website CW Scanner and provided to Guardian Australia reveals that within days, the supermarket chain raised prices on at least four key products. Because nothing says "we feel your pain" like a 33% markup on chicken.

The data shows that a 420g can of Woolworths "Mexican Style 3 Bean Mix" nearly doubled in price during the promotional period, jumping from 60c to $1 on 17 June, before dropping back to 60c on 17 August. Meanwhile, 350g packs of RSPCA-approved chicken breast fillets surged 33%, from $9 on 29 April to $12 on 5 May, then alternated between $9 and $12 twice more during the "freeze." After the promotion ended, the price plummeted to $4.20 on 17 August - because nothing pairs better with a price freeze than a post-freeze fire sale.

Woolworths declined to comment on the analysis, but it is understood the company justified the increases by claiming the previous prices were promotional, not the "standard shelf price." When the freeze was announced, CEO Amanda Bardwell said the supermarket wanted to help customers concerned about inflation driven by the war on Iran. "It's our promise that the shelf price you see on these items today is the most you'll pay for the next three months," Bardwell said in a 30 April press release. "We'll invest to absorb any extra costs that are agreed with suppliers on these products to make that happen." Apparently, "absorb" was code for "pass along."

Prof Jana Bowden, a marketing expert and chair of ethics at Macquarie University's business school, said raising prices after claiming they had been fixed was "akin to not delivering on the everyday consumer's interpretation of a 'price freeze' promise." She added, "How is the consumer expected to know what the start prices were before the campaign or even after the campaign started? No consumer walks into a supermarket with the insights of how the prices for the hundreds of products that they buy vary over a day, week, month or year - nor should they have to." In other words, shoppers aren't psychic, and they shouldn't need to be.

The analysis comes amid high scrutiny of pricing tactics used by Woolworths and rival Coles after landmark court cases. Woolworths is awaiting a verdict in a federal court case brought by the Australian Competition and Consumer Commission (ACCC), which alleges the supermarket misled shoppers with effectively fake discounts on its "Prices Dropped" campaign. Because why stop at one pricing scandal when you can have two?

Other items weren't spared. Before the promotion, Woolworths' 2kg bags of washed potatoes routinely alternated between $6 and $8. During the freeze, they cost $6 on 29 April, then went up to $8 on 6 May. A 12-pack of own-brand fresh cinnamon donuts rose from $3 to $3.50 on 6 May, before returning to $3 on 18 August. It's like a rollercoaster, but with more carbohydrates and less thrill.

Bea Sherwood, senior campaigns and policy adviser at Choice, said the advocacy group regularly hears from confused consumers. "Prices have changed so much over recent years and we're seeing them continuously increase, so having an understanding of what a regular shelf price is is not something we can expect consumers to stay on top of," Sherwood said. "When Woolworths or Coles say something is a standard price, we don't have the transparency to understand how they've come to that." In short: the only thing freezing is the consumer's ability to keep up.