Immigration reform that focuses exclusively on enforcing laws against illegal immigration would cause a sharp rise in food prices, particularly for fruit and vegetables, a new study warns.

The report, commissioned by the National Farm Bureau, said consumers would bear the brunt of such a measure, with prices rising 5 to 6 percent as farmers pass on some of their costs.

The farm sector's heavy reliance on undocumented immigrants for its workforce makes it particularly sensitive to the effects of immigration reform, especially if an "enforcement only" approach is adopted. Alternatives would combine enforcement with a path to citizenship or an expanded guest worker program.

The report, released on Monday, comes as the U.S. House of Representatives wrestles with whether any form of immigration reform will be on its agenda this year. A broad package passed the Senate last year.

"Given the reform proposals advanced to date, there is little doubt that increased enforcement" will be a major part of any reform package, the report observes. "Increased enforcement" is defined as strengthened border security and expanded enforcement of existing laws, combined with more aggressive use of deportation.

Without a path to citizenship and no guest worker program, agriculture would face the loss of 50 percent or more of its hired workforce, the report warns. It estimated that 525,000 — or half — of all hired farm workers are undocumented immigrants.

Fruit production would drop by 30 to 61 percent under the enforcement-only option, and vegetable production would decline by 15 to 31 percent, according to the report. Livestock production would fall by 13 to 27 percent.

U.S. Sen. Al Franken, D-Minn., has been particularly vocal in advocating for broadening the guest worker visas, which last no longer than a year. Franken and others have pointed out the importance of year-round workers for both the dairy and livestock industries, which have a considerable presence in Minnesota.