'Because of the different inspection results that have created public misunderstanding and concern about food safety, I have decided to resign to take full responsibility,' Mr Lin said after submitting a written resignation to Mr Liu.

Observers saw the move as a bid to ease growing public disapproval of the performance of Taiwanese President Ma Ying-jeou's government.

Hsiao Tung-min, head of the Bureau of Food Safety, had also resigned to take administrative responsibility, Ms Shih said.

The resignations came a day after the Department of Health ordered all food and beverages that used mainland dairy ingredients and vegetable-based proteins to be taken off the shelves by Wednesday night.

The order was issued after six firms were found to have imported melamine-tainted products from the mainland, where authorities say 53,000 infants are sick after drinking milk formula tainted with the chemical that can cause kidney stones and lead to kidney failure. At least four have died.

The ingredients were used by Taiwanese food processors to make other products, which were sold to wholesalers and retailers in Taiwan.

But while local operators were removing tainted products from the shelves, the Department of Health changed the inspection criteria late on Wednesday night - which changed the inspection results.

Under the new criteria, foodstuffs would be considered safe if the melamine content was less than 2.5mg per kilogram. Two importers previously said to have imported tainted ingredients were spared as a result.

Mr Lin's deputy, Sung Yen-jen, said the new standard, which mirrors Hong Kong's, takes into account the fact some ingredients might have a trace of melamine from plastic containers or other industrial materials.

He stressed if a mooncake contained 2.5mg per kilogram of melamine, a person would have to consume 2,800 mooncakes a day to be poisoned.

But opposition Democratic Progressive Party lawmakers cried foul, pointing out the mainland does not allow food to contain 2.5mg per kilogram of melamine, or 2.5 parts per million. 'China has set the criteria for pig feed at 2ppm. Does that mean Taiwanese people are not as worthy as Chinese hogs?' asked DPP lawmaker Yeh Yi-chin.

Ruling Kuomintang lawmakers also criticised the government for managing the crisis poorly. 'With such a flip-flop, do you think the public would feel safe? In managing a crisis, the government gets zero points,' KMT lawmaker Lin Yu-fang said.

Another KMT lawmaker, Chiu Yi, said the crisis could be the last straw prompting a reshuffle of the cabinet.

Mr Liu later acknowledged there was an urgent need for the government to strengthen its crisis management ability.

Taiwan plans to send a team of health experts to the mainland on Sunday to try to gain a better understanding of the crisis and find ways to seek compensation. Beijing had agreed to allow the visit, according to Taiwan's Mainland Affairs Council.