"It was a very challenging period for the party and it is due to the loyalty of our party membership that we are in a position to look forward to a strong and successful future," Ball said.
NZ First went from having nine MPs in Parliament after winning 7.2 per cent of the vote in 2017 to being booted out altogether when it garnered just 2.6 per cent in October's election.
Ball said the party had begun working on "several particularly important areas of focus which include an election review", electorate planning and organising its AGM next year.
Ball said being appointed acting president was "a great honour and responsibility".
"I have been a member of the party for more than a decade with experience as a previous board member, vice-president, and Member of Parliament, and look forward to the year ahead for the party.
"On behalf of the board, I would like to sincerely thank all candidates, members and supporters for your hard work and loyalty throughout this challenging year."