TAIPEI (AFP) - Taiwanese authorities on Wednesday imposed a record fine of NT$6.32 billion (S$265 million) on nine independent power producers for manipulating prices, after a public outcry over spiralling rates.

The nine suppliers to state-owned Taiwan Power Co (Taipower) violated fair trade law by colluding with each other to prevent price adjustments during negotiations with Taipower from 2008 to 2012, the Fair Trade Commission said.

The commission slapped the companies with the record fine as their "illegal actions have seriously affected the order of the market," it said in a statement.

The case came to light after public complaints last year prompted by a steep hike in utility rates by the loss-making Taipower as it tried to address its financial woes.

Some lawmakers have alleged that independent power providers were making profits at the expense of Taipower, which has lost at least NT$132.2 billion since 2008.

Outrage over the utility hikes forced the then Taipower chief to resign and the government to split the increases of up to 40 per cent into three stages.