A group of 14 growers have issued a joint warning that some fruit and vegetables could rot unharvested this summer because of a shortage of people to pick them.

This could reduce the supply of produce and push up prices.

The warning came from farmers at the front line of the looming picker shortage, such as growers of some vegetables, strawberries, stone fruit, cherries and watermelons.

There have been weeks of warnings that the Covid-19 ban on Registered Seasonal Employer (RSE) workers could leave growers in the lurch, despite months of work and thousands of dollars of investment in getting the crops ready.

Last year, 14,400 RSE workers were approved for New Zealand.

This year, the only ones available are those who were unable to go home from last year because of travel restrictions into their own countries.

Horticulture New Zealand has protested this but believes a decision will have to wait until after the election.

Brett Heaps, who grows zucchini near Kerikeri, poured scorn on this.

"Crops don't wait [for an election]," he said.

"We have got to harvest now, it is critical."

Another signee of this warning letter was Stephen Darling, a cherry, apricot and apple grower from central Otago.

He agreed this problem could not wait.

"We know the government is aware of the importance of our crops, but time is slipping by," he said.

"The need for pickers is now."

The growers said incoming RSE workers could be put in quarantine here and could be chosen from countries with no reported cases of Covid in the first place.

Labour has said many times that the border must be kept secure for the sake of public health in New Zealand.

They have also cast doubt on the reliability of the official Covid-free status of several states listed by the World Health Organisation.

Pacific states like Vanuatu and Solomon Islands are among them, and they traditionally provide RSE workers to New Zealand.

The National Party has supported the principle of getting RSE workers from Covid-free countries.

The 14 signees of the letter said without having a core staff of experienced overseas workers, the crops would not get harvested, and consequential vacancies for New Zealanders with long-term jobs in the horticultural industry would not be available.

They also said picking was often hard physical work and was unsuitable for many of the people the Labour Party was trying to steer in its direction.

They also criticised the announcement of an inquiry into supermarket prices, calling it a hollow promise when as a result of the government's intransigence, early harvested crops would be rotting in the ground and prices would skyrocket due to lack of availability.

They added export markets could be lost.

"America's Cup sailors can come into the country; tractor drivers can come into the country; film workers can come into the country - but people who do the hard work of getting food to New Zealanders are apparently not 'critical" workers," the signees said.