British consumer goods maker Reckitt Benckiser has been fined 24 million euros (20 million pounds) by the German cartel office for fixing prices on laundry and dishwashing products with German rival Henkel.

The German cartel office said Henkel escaped a fine after acting as a whistle-blower and instigating the investigation in 2010.

The two companies coordinated price rises for their products over a period of years. Customers paid dearly for this, Andreas Mundt, president of the cartel office, said on Wednesday.

The authority said it had found four instances between mid-2005 and mid-2007 where Reckitt's German unit and Henkel fixed prices, such as by increasing prices for dishwashing products, all-purpose cleaners Cillit Bang and Bref and washing products Vanish Oxi Action and Sil.

In one of the incidents, the two agreed to reduce the sizes of the boxes for Calgonit and Somat dishwasher tablets, thus indirectly increasing the price per box by 13 percent, the cartel office said.

Reckitt's fine also included a penalty in a separate case in which consumer goods firms were fined for sharing sensitive information following a tip-off from U.S. group Colgate Palmolive.

The cartel office had already fined eight companies a total of around 20 million euros in 2008 in connection with that investigation.

A spokesman for Henkel said it had worked with the authorities following that case, and Wednesday's price-fixing fine for Reckitt came about as a result.

The fine was reduced after Reckitt -- which would not comment -- cooperated fully with the investigation, the authority said.

(Reporting by Victoria Bryan; Additional by David Jones)