The prime minister of New Zealand, Jacinda Ardern, has postponed the country’s general election by a month amid a spike in coronavirus cases.

The vote was due to take place on 19 September but will now be held on 17 October instead.

Ms Ardern said on Monday that the new date would allow parties “to plan around the range of circumstances we will be campaigning under”.

Earlier this week, the country’s largest city went back into lockdown.

The opposition National Party has argued the election should be delayed as restrictions on campaigning mean Ms Ardern had an unfair advantage.

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The restrictions were imposed on Auckland on Wednesday after a number of new infections were identified in the city.

The development shocked the country, which had recorded no locally transmitted cases for more than three months.

There are four “alert levels” in New Zealand, and Auckland has been on Level 3 since the new measures were announced. The rest of the country is on Level 2.

Before the new cluster was identified, the government had lifted almost all of its lockdown restrictions, which were first imposed in March.

An early lockdown, tough border restrictions, effective health messaging and an aggressive test-and-trace programme had all been credited with virtually eliminating the virus in the country.