Sheridan said Ardern's one big policy win is suppressing Covid-19.
"Before Covid came along, Jacinda Ardern was behind in the polls, and she hadn't delivered on her election, and her centre-left outlook was not helpful to the New Zealand economy."
Sheridan said the Covid recovery is not that impressive, as many other Pacific Island nations have achieved low Covid-19 cases.
He also said he believed Ardern's international appeal is purely symbolic.
"Time magazine and Vogue and so on, they're not saying 'look what a wonderful job she's done with the economy', otherwise they'd have made John Key a celebrity."
In his Wednesday column for The Australian, Sheridan said in "real policy terms" Ardern's achievements were "thin or negative".
"Ardern has done three positive things. She has just about eradicated Covid-19. She has navigated the politics of the virus so well she stands on the brink of electoral triumph. And she responded with moral clarity and decency to the Christchurch massacre," Sheridan wrote.
"However, she has still been a poor Prime Minister, elected almost by accident under the Byzantine protocols of her country's eccentric electoral system, though she won far fewer votes than the National government she replaced.
"No international halo is so shabby, or so fraudulent, as that worn by New Zealand Prime Minister, Jacinda Ardern. Politically she resembles Dan Andrews. They excel in woke gesture and progressive symbolism. Their achievements in real policy terms are thin or negative.
"It goes without saying that her achievements should never be diminished because of her gender or age; she was only 37 when she became Prime Minister. But undoubtedly part of the international Jacindamania comes from the fact she is a young left-wing woman who gave birth in office and took maternity leave. That is all wonderful but it has no bearing on policy achievement.
In the column Sheridan also warned of a political shift to the left doe New Zealand if Labour wins the election.
"Validated by a swooning international media, unchallenged by a tepid and under-resourced local media, she has sold the narrative that her government has saved NZ. With Peters gone, and the Greens more influential, she will move left in her second term, presaging a lost decade for our beloved cousins across the ditch. One consolation: the best of them will come here."
