Laulala, who's been with the Ministry of Justice at the Manukau District Court for more than a decade, addressed Ardern at the conference for the union for public servants, the Public Service Association (PSA).
Laulala is involved with the PSA's women's and Pasifika networks and said she'd written to the ministry's chief executive "time and time again" urging him not to forget about them.
"I said, 'Do not forget Pasifika women are at the bottom of the pay scale'."
Ardern told Laulala she was not going to argue with her and the Government knew the pay gap at the Ministry of Justice where she worked was among the worst.
"There is nothing defensible about a pay gap, a gender pay gap, a pay gap that's demonstrably clear around ethnicity. There's no justification at all."
Ardern said the Government had made progress on pay equity issues and asked the union to help it find the people whose need was overwhelming but who didn't have a collective voice.
Last term the Government passed the Equal Pay Amendment Act which allows workers to make a pay equity claim without going to court.
"There's no need to convince us, there's no need for ongoing hui but there is a need for us to keep going," Ardern said.
Pacific women are the worst paid employees in the public service and in 2019 made on average $64,600 while Pākehā men made an average of $91,400.
According to the Ministry of Justice's pay gap action plan in February its pay gap is 12.1 per cent - down from 18.3 per cent in 2015.
The average pay gap between the average salaries of men and women across the public service is 10.5 per cent - down from 14 per cent in 2015.
The Ministry of Justice is in the final stages of negotiating a new collective agreement with the PSA which would see the starting pay rates increase from $44,000 to $49,000.
It comes after thousands of ministry workers striked in 2018 because the pay offering didn't do enough to close the pay gap.
The Ministry of Justice's general manager of people and performance, Jo Hickling, said in a statement to the NZ Herald said the Prime Minister "is right".
"We know there is a gender pay gap at the ministry, and we are committed to addressing this through our Gender Pay Gap Action Plan.
"We are working constructively with the PSA, and together we are on a journey to tackle this issue."
Public Services Minister Chris Hipkins also addressed the PSA's conference, held at Te Papa, and said one of his key priorities this term was making the sector an exemplar employer.
That included paying the public service's contractors a living wage and welcoming pay parity and pay equity claims.
"I'm not going to rest until the gender pay gap is closed completely," Hipkins said.
PSA national secretary Kerry Davies said they were very pleased to hear the Prime Minister reaffirm her commitment to equal pay for women, Pasifika and Māori workers.
"Our members are extremely passionate about this issue, and they seized the chance to raise it directly with her.
"There is still a long way to go and underpaid, undervalued workers are tired of waiting.
"Ministry of Justice workers have been at the bottom of the heap for too long, and so have Pasifika women throughout the public service."
The Ministry of Justice's pay gap action plan said closing the gender pay gap was one of its strategic priorities and ensuring women's pay reflected their skills, efforts and responsibilities and wasn't negatively affected by their gender was a fundamental human rights.
What causes the gender pay gap?
The Ministry of Justice says a number of factors can contribute to the gap, including: • More men in higher-paid roles and/or more women in lower-paid roles of an organisation • Undervaluing work predominantly or exclusively performed by women • Men progressing more quickly than women • Men receiving (on average) higher starting pay, discretionary pay, pay increases or performance ratings • Disproportionately slower career or pay progress for employees who take caregiving breaks, or who work part-time or flexibly.