Prime Minister John Key said the election result on Saturday would be a lot closer than people expected and the potential for a Labour-led Government was real.
He made the comments as he released what he called National's action plan, detailing the party's priorities on the economy, welfare, law and order, education, health and on rebuilding Canterbury.
Mr Key appeared worried that recent polls showing National could comfortably govern alone could lead to complacency among his supporters.
"Under MMP you can stack up the parties and the potential for a Labour-led stack of minority parties is very real.
"The more complex the stack, the more expensive it will be."