Lawmakers on Wednesday passed legal changes that officials say will better protect labour rights for part-timers.

Workers are currently only entitled to benefits like paid rest days and annual leave if they are employed under a continuous contract.

Such a contract is defined as working four straight weeks for at least 18 hours a week, otherwise known as the "418 rule".

The change to a "468 rule" now, means people working 68 hours over four weeks will be considered as continuously employed.

Labour minister Chris Sun said the change will take effect six months after the new law is gazetted.

He told lawmakers that as there have been changes in the labour market, the government initiated the amendment process three years ago, to improve the rights of workers.

"This legal amendment is allowing greater flexibility in calculating work hours and lowering the threshold for what qualifies as a continuous contract, making it easier for employees to meet the revised continuous contract requirement," Sun said.

"There will also be fewer disruptions to continuous employment in the event the workers' hours occasionally fall below the threshold in a certain week."

Some lawmakers who own businesses expressed concern about the changes.

Noting that employers often are the ones making roster decisions, Sun sought to allay their concerns by saying that the rule change would not give workers a bigger say on their working hours.

Sun added that other clauses under the Employment Ordinance are unchanged, and workers who already qualify as working under a continuous contract are not affected by the bill's passage.