Thailand's premier urged the kingdom's rival political factions Wednesday to work together to tackle the worst floods in decades, as the opposition called on her to declare a state of emergency.

"Today I will frankly tell you the truth. I have left no stone unturned in this crisis but I cannot solve it alone. I need cooperation from all sides," a teary-eyed Prime Minister Yingluck Shinawatra told reporters.

"Let's set aside politics. We must work to restore people's morale," added the sister of fugitive former leader Thaksin Shinawatra.

Yingluck, a political novice who has been in office for barely two months, has been criticised for a lack of clear information on the disaster, which has killed more than 300 people around the country.

"It's a crisis of leadership," said Pavin Chachavalpongpun, a former Thai diplomat and expert at the Institute for Southeast Asian Studies in Singapore.

"Yingluck has been very slow in responding to the crisis. At the beginning there was no integrated policy, many different ministers said different things, causing a lot of panic," he added.

The premier also faces a dilemma over whether to block the floods to protect Bangkok, the country's economic and political heartland, or release more water upriver to ease the burden on hard-hit central areas.

The opposition Democrats are calling on the government to declare emergency rule, as they themselves did when in power to deal with political unrest in the capital last year, leaving dozens dead in a military crackdown.

"The situation is getting worse and seems to be out of control because people have panicked and destroyed dykes, so if government imposes emergency law it would help control people," said Democrat spokesman Sakoltee Pattiyakul.

The laws would give the authorities the power to forcibly evacuate people or ban them from certain roads or other places. The government has said the decree is not necessary and would hurt investor confidence.

Pavin said the opposition was at fault too for proposing the emergency rule.

"What on earth for? When you declare an emergency decree you give power to the military," he said.

Authorities in the low-lying capital have been racing to reinforce barriers with sandbags in an attempt to protect the city of 12 million people.

Bangkok governor Sukhumbhand Paribatra -- a Democrat -- warned that seven districts in northern and eastern Bangkok were at risk of inundation because of a broken dyke.

He advised residents in those areas to unplug electrical appliances, move belongings to higher ground and study the city's evacuation plan, saying they had 24 hours to prepare for possible flooding.

Three months of heavy monsoon rains have damaged the homes and livelihoods of millions of people, mostly in northern and central Thailand, and have forced tens of thousands to seek refuge in shelters.

Currently about one third of Thailand's provinces are affected by the floods, which are several metres deep in places.

An adviser to the country's National Disaster Warning Centre, Admiral Kohlak Charoenruk, said the floods should be allowed to flow through Bangkok.

"If government keeps blocking water it will cause epidemic diseases and a humanitarian disaster. The government needs to release water into the sea as soon as possible," he told AFP.

Commerce Minister Kittirat Na-Ranong said more than half a million people have been left without work after many factories were inundated, but he was optimistic that foreign investors would not abandon Thailand.

Most of Thailand main tourist attractions -- including the southern islands -- as well as Bangkok's main airport have so far been unaffected.