The Government is to extend its control of spending by young beneficiaries to all teen parents and many 18 and 19-year-olds.

Prime Minister John Key this afternoon announced the Youth Service payment card, money management, and intensive support and guidance regime which currently applies to 16 and 17 year old beneficiaries would be extended if National was re-elected.

Social Development Minister Paula Bennett many young people weren't getting the "wrap around service" they needed.

The extension would affect about 5700 young people and would cost about $10 million to $15 million a year.

Under the new policy, Work and Income will assess all under 20s who are seeking a benefit.

Ms Bennett said "self-motivated young people who are not likely to spend long on a benefit will continue their job search with the help of Work and Income, just as they do now.

"Others with more complex needs will be referred to a youth service provider, where they will receive intensive support and guidance, together with budgeting support and the use of a payment card."

There would be no change for young people receiving the Supported Living Payment.

National introduced the Youth Service approach in 2012 for 16 and 17 year olds, and for teen parents up to 18. The service involves mentoring and advice, money management, and budgeting and parenting obligations.