The popularity of Whittaker's new chocolate block has caused all flavours to run low.

The 250g Hazella block was released last month.

But a Whittaker's spokesperson says the demand for the chocolate, which was revealed early after Countdown's online shop advertised it before its release date, has been higher than expected.

The block is 'currently out-of-stock across some retailers due to the unprecedented demand,” she says.

'But we're making lots more and will have it out to retail outlets as soon as possible.”

Because the Hazella blocks are made on the same production line as the other block flavours, it has an effect on all the Whittaker's chocolate products, she says.

'This has had an impact on stock levels overall, but everything should be back to normal soon.”

Foodstuffs, which operates Pak'n Save and New World, says some of its stores have low stock levels of 250g blocks.

Hazella is the second block Whittaker's released this year. In July its plant-based block, Oat Milk, was dubbed the worst kept secret after a New World online shopping advertisement accidentally appeared on Google two weeks early.

-Brianna Mcilraith/Stuff.