Teen parents will be obligated to attend a parenting course, enrol their children with a primary health organisation and have them attend early childhood education, and complete health checks.
Those deemed eligible will not be able to opt out of the youth service.
The Social Security (Extension of Young Persons Services and Remedial Matters) Amendment Bill passed its first reading last night by 105 votes to 10.
Labour MP Sue Moroney said the party would supported the bill to the select committee stage, where she expected "serious reservations" to be examined.
"The part that we are very concerned about ... the idea that they are going to be put through some kind of risk-rating process, fills me with dread."
Ms Moroney said risk-rating approaches in other areas of government such as in the setting of ACC levies on motor vehicles had been shambolic.
Extending the youth service was part of National's election manifesto, and Social Development Minister Anne Tolley said the programme, introduced in 2012, was having a greatly positive impact on many young people.
"Over the year to March 2014, 70 per cent of the youth payment recipients were able to live independently, rather than moving on to an adult benefit."
Green Party MP Eugenie Sage said the party opposed the bill because of the paternalistic approach it took.
"We also have quite serious concerns about forcing single young people up to the age of 20 into a model with quite onerous accountability, based on the state's identification of them as at-risk young people."
There was a risk of arbitrary and unfair decision-making, Ms Sage said, and could lead to young people feeling stigmatised and resentful.
"This is a huge infringement on human rights by having the state determine which category you fall into, and therefore which services you should have access to."
NZ First MP Darroch Ball said his party supported sending the bill to a select committee as it was fundamentally well intentioned. However, there were concerning areas, including the fact participation in the youth service would be mandatory.