TOKYO (AFP) - Japan's hotels, restaurants and food shops were being warned on Wednesday over dishonest labelling amid a growing scandal that is threatening to undermine the country's reputation for safe, high-quality produce.

The direction comes as top department stores became the latest Japanese firms to admit they had been selling food with labels falsely claiming high-quality or expensive ingredients.

"It's extremely regrettable as it seriously undermines consumer confidence," Chief Cabinet Secretary Yoshihide Suga told a regular press conference, speaking about the widening scandal.

"The Consumer Affairs Agency will take strict actions under the law (against misleading representations)," he said.

Mr Suga, Prime Minister Shinzo Abe's right-hand man, was speaking after luxury department store chain Takashimaya admitted that for years labels claiming the use of top-of-the-range prawns or freshly-squeezed orange juice sat on produce made with inferior ingredients.

For example, the department store used giant tiger prawns to make a "Japanese tiger prawn" terrine, sold under the luxury French brand Fauchon.

Japanese tiger prawn is widely considered a top shrimp and one that can command premium prices in this seafood-loving nation, while giant tiger prawns are more widely available.

The company insisted that the wide range of false labelling were honest mistakes, echoing excuses from a string of hotels that had long served meals claiming quality ingredients that were not part of the dish.

Whatever their excuses, "the fact remains they deceived consumers by making their products seem more luxurious than in reality," the Asahi Shimbun said in a front-page commentary, calling for tougher regulations.