British Prime Minister Theresa May congratulates Jacinda Ardern on being Prime Minister-designate

British Prime Minister Theresa May phoned Jacinda Ardern last night to congratulate her. Photo / AP

Theresa May is the latest world leader to wish Jacinda Ardern well on becoming Prime Minister-designate.

Ardern told the Herald the UK Prime Minister phoned her last night.

Australian Prime Minister Malcolm Turnbull offered his congratulations in a phone call on Thursday night after New Zealand First leader Winston Peters announced his party would form a coalition Government with Labour and the Greens.

Ardern said the conversations with May and Turnbull focused on the importance of New Zealand's relationship with the two nations and that world issues hadn't been discussed. The Premier of Niue had also congratulated her via a message, she said. Ardern's parents live in the small island country, where her dad Ross is the High Commissioner of New Zealand.

Ardern said she was expecting phone calls from two other world leaders during Labour Weekend, but wouldn't be drawn on who they'd be from.

"I wouldn't want to speculate and then have them not happen."

She told the Herald her plans for the holiday weekend involved "mostly work" and said she did not believe she'd be attending any public events during the next few days at this stage.

"There's nothing really interesting to report, I'm mostly doing work over the weekend."

She confirmed that US President Donald Trump is yet to speak to her directly, however his administration has sent its congratulations.

A statement issued by the US Department of State today said the relationship between the two countries was strong and New Zealand was one of the superpower's "closest friends and partners.

"We look forward to working with New Zealand's new government and continuing to cooperate on our shared interests in the region and worldwide," the statement said.

Canadian Prime Minister Justin Trudeau issued a statement on Thursday expressing his congratulations to Ardern for forming the next New Zealand government.

"I look forward to working very closely with Ms. Ardern," he said.

Canada and New Zealand already co-operated closely at the United Nations, the Commonwealth, the Asia-Pacific Economic Cooperation Forum, and the Association of Southeast Asian Nations Regional Forum and would look for new opportunities to strengthen ties, the statement said.

"We have the opportunity to bring our two countries even closer together as we tackle the common issues that face both Canadians and New Zealanders.

"Whether it is addressing climate change or deepening trade relationships that create real benefits for everyone, Canada and New Zealand have a great deal to share and learn from each other."

Meanwhile, New Zealand First leader Winston Peters said his party was selecting its Ministers before the new government would be sworn in next week and its agreement with Labour was soon to be published.

"As stated on Thursday, the agreement is a summation of the policies that survived the negotiations. As the song says, 'You can't always get what you want'," Peters said in a Facebook post.