Adams said the opening and closing addresses were an outdated format and declining audiences showed that voters were not being engaged.
During opening addresses in the 2014 general election period, TVNZ's audience numbers fell by a quarter.
Adams said legislation introduced today recognised the growing use of digital and online media.
"I hope that by giving parties more flexibility in how they communicate their messages, more voters will engage in the electoral process," she said.
"Parties will continue to be able to spend their own money on online advertising while funding for television and radio advertising remains limited to the funding allocated by the Electoral Commission."
To make up for the reduction in free broadcasting time, the Government lifted funding for each party from $2.8m to $3.6m.
Rules about parties' election spending, which is restricted according to the size of each party, will not change as a result of the legislation.