A plan by Cadbury to cut the size of its 220g chocolate blocks while keeping the same retail price has left a bitter taste in the mouths of sweet tooths around Australia.

Cadbury confirmed its family size blocks, which are manufactured in Hobart's northern suburbs, would be reduced to 200g.

In a statement, the Claremont-based chocolatier blamed rising manufacturing costs for the size reduction.

The company said it was being upfront about the change before the smaller chocolate blocks hit supermarket shelves.

"We had to make a choice - increase the price we recommend to our retailers or change the size a little," it said.

"We wanted to maintain the taste and quality while keeping Cadbury family blocks affordable as we know how important it is to people to maintain their shopping budget."

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But thousands of chocolate lovers on Cadbury's Facebook page and on Twitter were unimpressed, blaming everything from corporate greed to Halal certification.

The number of comments climbed steadily, reaching 2,800 just hours after the announcement was posted at 3:00am (AEDT).

Some were thanking the company for being upfront and saving local jobs but others were scathing.

"Your logic is that if you start charging $4 for five rows people will still buy it? I know I won't," one person wrote on Facebook.

"So the slogan will be ... with 3/4 glass of milk in every block. Boo to you Cadbury. What a load of rubbish," another person wrote.

It it understood Cadbury has been struggling with the increasing cost of imported cocoa beans recently, asking about 300 of its Hobart-based staff to take a longer summer break in a bid to save money.

Cadbury employs about 500 workers at its Claremont plant.

The company was promised $16 million during the 2013 federal election campaign, which has yet to be handed over.

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