Deputy Prime Minister and New Zealand First Leader Winston Peters has warned unionists that any future attacks on the Government won't work.

He also called out unions for sitting on the sidelines under the previous National Government when it came to workers' rights, but who are now attacking the current Government.

Peters also took credit for the increases in the minimum wage, saying New Zealanders had his party to thank, not Labour.

Speaking at the Council of Trade Unions' (CTU) biennial conference this afternoon, Peters challenged unions, while he reinforced New Zealand First as a centrist party.

"We are making sure this is not a right-wing Government, nor a left-wing one," he told those gathered.

"We preside over a solutions-focused, future-orientated Government rooted in tangible facts and not spurious economic theory."

He then took aim at the unions, asking what they were doing in the nine years National was in power.

"While conditions of much of the workforce deteriorated under the previous Government for nine-long years with stagnated wages and a rising cost of living getting out of control, we didn't see enough action from you," he said to unionists.

"Now … we are being attacked by the union movement in this country? You can have your views but I'm here to say standing in the middle of the [political] spectrum, that it won't work.

"And I say that as someone who was a union delegate."

Peters also took credit for the minimum wage increases so far delivered and promised by the Government.

"It is not our coalition partner' policy, it's ours – unlike Shane Jones, I won't ask you to start cheering now."

The Government increased the minimum wage to $17.70 this year and it will rise to $18.90 next year, before hitting $20 an hour in 2021.

Speaking to media after his speech, he said New Zealanders had his party to thank for that increase.

In fact, he revealed that New Zealand First had gone to a much higher figure than Labour campaigned on.

"You will not find anyone arguing that it wasn't us that set the higher figure."

He would not, however, reveal what the figure NZ First was lobbying for during the 2017 coalition negotiations.

"But where it was set in the end was a NZ First requirement."

The Fair Pay Agreement legislation is still being hammered out in Parliament.

Asked if the Fair Pay legislation would be in place before the 2020 election, Peters said: "We will have an answer for you in a matter of months".