Opposition lawmakers earlier formed a human barricade in parliament to stop the conservative ruling Grand National Party passing the revised law on what are known as "non-regular" or temporary workers.

The country has an estimated 5.3-million temporary workers, with bosses unwilling to employ them on a permanent basis.

Strict labor laws give permanent workers greater protection against dismissal, higher pay and other benefits such as insurance.

The previous liberal government in 2007 passed a law requiring bosses either to permanently hire or to fire temporary staff who have worked for two years.

However, the law expired on July 1 and newspapers say some temporary staffers have already been laid off.

Amid the continuing economic downturn, there are fears many more companies will follow suit.

The government and ruling party say up to one million jobs could be at risk, while the opposition and labor unions put the figure at 400,000.

"The National Assembly must act quickly," Lee said at a joint meeting of government officials, lawmakers and business representatives.

"The fundamental issue is how to secure labor market flexibility and we need a comprehensive approach."

The government proposes a one-time 18-month extension to the time limit in the 2007 bill, while a permanent solution is worked out.

The main opposition Democratic Party says this will only increase the number of workers without proper benefits. It staged sit-ins last month to block the legislation.

Labor unions urged the government and companies to give non-regular workers job security.

"If the revision is introduced to the National Assembly, we will immediately launch a general strike," the Korean Confederation of Trade Unions said in a statement this week.

The Federation of Korean Industries (FKI) called for a new law that would bring greater flexibility to the labor market.