United Future leader Peter Dunne is going to ask the Government to clean up the Clean Slate Act.
He says it's too rigid in practice and leaves too many people with old criminal records.
Mr Dunne says it was designed to allow minor convictions to be wiped from a person's record after seven years to enable them to get on with their lives.
But he knows of cases where people with minor offences from over 20 years ago, and with no subsequent offending, still have these on their record because they involved a custodial sentence, no matter how small.
"I don't think the law was intended for people like these, who have stayed out of trouble for often up to three times the seven-year time limit the Clean Slate Act requires," he said.
"They now find their long-distant past catching up with them when it comes to police clearance for employment."
Mr Dunne says he's going to write to Justice Minister Amy Adams asking her to review the legislation.