Migrants in Denmark will be told to complete 37 hours' work a week in order to receive welfare benefits, the government has said.

Migration and integration have become key issues for voters in Denmark, which boasts some of Europe's toughest immigration policies.

The Danish government, which has set a target of zero asylum applications, said the plan was designed to help migrants assimilate into society.

"We want to introduce a new work logic where people have a duty to contribute and be useful, and if they can't find a regular job, they have to work for their allowance," Prime Minister Mette Frederiksen told reporters.

"For too many years we have done a disservice to a lot of people by not demanding anything of them," she added of the plan, which needs to be approved by lawmakers.

Mai Villadsen, spokeswoman of the left-wing Unity List, condemned the announcement as misguided.

"I'm afraid this will end up as state-supported social dumping, sending people into crazy jobs," she told broadcaster TV2.

Initially, it will be a requirement for those who have been on benefits for three to four years, and who have not attained a certain level of schooling and proficiency in Danish.

Working hours will be a minimum of 37 hours a week, Ms Frederiksen said.

According to the government, six out of 10 women from the Middle East, North Africa and Turkey do not participate in the Danish labour market.

The plan says it aims to integrate 20,000 people by pushing them to find some form of work, through local government offices.

"It could be a job on the beach picking up cigarette butts or plastic... (or) helping to solve various tasks within a company," employment minister Peter Hummelgaard said.

"The most important thing for us is that people get out of their homes," he added.

Ms Frederiksen's government, in power since 2019, has set a target of zero asylum applications, which have already fallen. Just 851 were received between 1 January and 31 July this year.

According to official statistics, 11% of Denmark's 5.8 million people are immigrants, and 58% of those are citizens of a country that Copenhagen classifies as "non-Western".

Last April, there were protests in Copenhagen against the Danish government's plan to deport Syrian refugees after Denmark refused to renew their residency permits.