Farmers still need up to 40,000 workers to help bring the harvest in this summer despite an 'overwhelming' response to hiring campaigns.
Defra launched the initiative 'Pick for Britain' last month to bring workers and employers together as the impact of Covid-19 leaves a diminished workforce.
From pickers and packers, to plant husbandry and tractor or forklift drivers, there are a wide range of roles available for furloughed employees.
Prince Charles backed the government campaign earlier this week, saying that the country needed an 'army of people to help'.
Elsewhere, three UK agricultural labour providers – Concordia, HOPs and Fruitful – launched the 'Feed the Nation' campaign in March.
But Tom Bradshaw, vice president of the NFU, told The Guardian that the difficulty had been in turning 'pickers that stick' - workers that would 'turn up day in, day out'.
The Pick for Britain website had had over 100,000 hits from unique visitors, Mr Bradshaw told the paper, and the latest estimate from April was that 25% to 30% of pickers on farms were British.
But Mr Bradshaw said: “We have got 20,000 to 40,000 more workers to find and those are going to be difficult.”
He added that farm businesses were still expecting eastern European workers to come to the UK but Covid-19 quarantine rules were causing industry uncertainty.
The government is expected to announce plans for any passengers arriving in the UK by plane to provide an address where they would self-quarantine for two weeks.
Mr Bradshaw warned that if this was applied to seasonal workers it could create a 'huge shortage'.
It comes as Waitrose and ITV recently joined forces to help recruit British farm pickers in support of the government's campaign.
The broadcaster's primetime TV advertisements urge the public to get involved and drive potential applicants to the Pick for Britain website.