More than 700,000 people have signed up to the Government's KiwiSaver as the retirement savings scheme celebrates its first birthday today.

Finance Minister Michael Cullen said latest figures showed 718,000 people were now enrolled in KiwiSaver, compared to a forecast 275,000 people after one year.

Dr Cullen no one predicted the high level of take up a year ago.

"Certainly no one would have predicted that we would have around 200,000 KiwiSavers under the age of 25 -- those people who still doubt KiwiSaver will lead to net new savings need to get to grips with these numbers."