Nearly 22,000 Romanians and Bulgarians are employed each year under the seasonal agricultural workers scheme - but this will close when access restrictions are lifted at the end of 2013.
The Migration Advisory Committee (MAC) found that the British horticulture sector could shrink if farmers fail to find replacement workers, which could trigger a surge in labour costs and ultimately higher prices for consumers.
Professor David Metcalf, MAC chair, said the Government should consider proposals for a new scheme that targets non-EU workers, in particular in countries which have a high number of agricultural students, such as the Ukraine.
Mr Metcalf told a press conference that if the labour supply "dwindled" once the scheme closed to Romanians and Bulgarians, operators may have to "drive wages up" to secure staff. He said: "In those circumstances, therefore, it's possible that supermarkets would charge higher prices for their celery and strawberries and so on."
He added: "It's very important to emphasise that, if we did have a replacement source, the implication is that horticulture is a favoured sector. It gets a supply of cheap labour, reliable labour and, more importantly, hired labour which is not available to any other sector. The only way that we should have a replacement scheme is if such a scheme would help horticulture thrive in the long run and the evidence from stakeholders is that it would do."
The MAC said a lack of seasonal workers was a medium to long-term risk, with British farmers likely to be able to recruit a sufficient number in the first one to two years after the working restrictions on Bulgarian and Romanians are lifted.
Temporary curbs were imposed on Romanians and Bulgarians in 2005 to protect the British labour market, but they expire in December and under EU laws cannot be extended. The Government has refused repeated demands to publish or commission estimates of the numbers expected to enter Britain in the face of unofficial research predicting as many as 50,000 people arriving from eastern European countries each year.
A Home Office spokeswoman said: "We are grateful for the MAC's report and note its conclusion that there is little evidence the supply of seasonal labour will decline in the next one or two years. We shall consider the MAC's advice very carefully, however in general we want to encourage employers to recruit from the resident labour market where possible."
- What do farmers and executives have in common? Crippling debt
- Job trends 'a cause for concern'
- Policies 'driving workers abroad'