However, Ms Robertson's work to secure a passport for a Kiwi friend of the touring star has resulted in a probe by New Zealand's Internal Affairs Minister.

Fred Again.. toured New Zealand over the last week, playing shows in Wellington, Auckland, and the Coroglen Tavern, a pub in the remote Coromandel Peninsula.

For the Coroglen Tavern gig, he threw out a call on his Instagram for warm-up acts, picking Wellington DJ MESSIE for the show.

Fred Again.., real name Fred Gibson, was so impressed with MESSIE, real name Tessa Hills, he wanted her to open for him at a huge stadium show in Perth this weekend.

"After seeing her play at the Corgolen Tavern last night I went straight up to her and invited her to play with us at our show on Saturday, the last show of this whole tour and the biggest one we'll have ever done," he posted.

The only problem: Ms Hills didn't have a passport to travel to Australia.

"Is there anybody that can help expedite this to make this absolute dream possible?" he posted on Instagram.

"Please, please and thank you (and sorry for being so last minute)."

A day later, the problem appeared solved.

"Thank you so much to Maria Robertson and her son!," Fred Again.. posted, along with a screenshot of a message from Ms Robertson's Instagram account "beautmum".

"I'm the Deputy Chief Executive at Internal Affairs," Ms Robertson said.

"My son got in touch with Tess after seeing your post, Tessa got in touch with us, she's made her application and we are sorting it with her.

"We love your music and we are thrilled you are backing one of our own to support your gig."

While this might otherwise be considered a good news story, given up-and-coming MESSIE's big break, Internal Affairs Minister Brooke Van Velden smelled impropriety.

Ms Van Velden - who said she followed Fred Again.. on Instagram but was not familiar with his music - asked her department for a please explain.

"I've only seen what's happened on social media but I do not believe it's appropriate for any official ... to be letting other members of the public know about passport applications, no matter how famous a person may be," she said.

"I'll be asking questions of officials within the passport office.

"Every citizen should be entitled to the same treatment."

The Ministry of Internal Affairs declined to answer AAP's questions but later responded with a brief statement.

"The minister has made her expectations clear. The department agrees with the minister's statements, and we are working to meet her expectations," department chief executive Paul James said.

Fred Again.. has sold out shows in Australia within minutes, playing a range of "pop-up" last minute gigs alongside stadium performances.

Australian Associated Press