Growers are increasingly concerned about workforce shortages despite having robust Covid security plans in place, the NFU has warned.
It was announced last week that more than 10,000 people who work in the UK food supply chain will be exempt from isolation rules if they are 'pinged' by the NHS Test and Trace app.
Defra Secretary George Eustice said that the government had made a special exception for the food industry for 'very obvious reasons'.
But fears continue to grow for large parts of the economy due to the so-called 'pingdemic' crisis, with a record 600,000 people in the week to 14 July being asked to self-isolate by the app.
Responding to the announcement that some food workers can apply for exemptions from isolating, the NFU said that it didn't go far enough.
The union has called for more measures to avoid disruption further down the chain, particularly for those who can 'offer more Covid security while keeping food supply moving.'
Vice president Tom Bradshaw said: “It is important to think about the whole food supply chain right back to farm because they produce the food that keeps processing plants and distribution centres going."
He said some farming businesses who had robust Covid-19 security plans in place on-farm were 'increasingly concerned' about workforce shortages.
This was particularly true as the rise in Covid cases coincided with the start of harvest, he said, when the picking and packing of fruit and veg is in full swing.
It comes as Defra confirmed on Sunday (25 July) that it had contacted 500 key food processing sites that had been identified for daily contact testing.
According to a report by the BBC, it is understood that testing will be rolled-out to key food chain sites, which will be joining large retailer depots as part of the initial phase of the testing programme.
The number of job roles that are exempt from isolation is also understood to have been broadened to include roles such as forklift drivers and dispatchers, the BBC said.
But the British Meat Processors Association (BMPA) recently warned that key details were still missing, along with a lack of clear guidance on how the rules would apply to individual companies and workers in the sector.
The body said: "We urgently need government to publish more information giving clear, unambiguous guidance on which sites are exempt, which job roles qualify for exemption and exactly how these new rules will be applied.
"We also question the government’s decision to end the provision of free lateral flow testing kits to companies last Monday just as the ‘pingdemic’ started to take hold.
"This just makes it more difficult and more expensive for companies to provide workplace testing and will inevitably start filtering through into higher food prices," the industry body added.