By Lesley Clark

Delivering a victory to farmworker groups that complain of paltry wages on Florida farms, senators said Tuesday they'll ask federal investigators to determine whether migrant farm workers are being paid as much as the tomato industry claims.

The call to have the Government Accountability Office investigate came as Sens. Edward Kennedy, D-Mass., and Bernie Sanders, I-Vermont, pledged to back efforts to boost pay and improve working conditions for thousands of migrant workers picking tomatoes in Immokalee and throughout Florida.

''This is the beginning, this is not the end,'' said Sanders, who toured the Collier County farming community in January and said he found the living conditions for workers ''deplorable.'' He said the committee was likely to push for greater protection of farmworkers, including changes to federal trafficking statutes.

Sanders also questioned the tomato industry's contention that tomato pickers make an average of $12.50 per hour. Most farms guarantee workers at least a minimum wage of $6.79, but pay them based on the number of buckets picked. For every 32-pound bucket, the worker gets a token typically worth 45 to 50 cents.

''We have broken ground on this issue,'' Sanders said. We are going to stay on this issue.''

The hearing came as tomato growers, represented by the Florida Tomato Growers Exchange, have scuttled efforts by the Coalition of Immokalee Workers to get fast-food chains to agree to pay an extra penny per pound more for their tomatoes.

Taco Bell agreed to pay the extra penny and did it for one year. McDonald's agreed, but has not yet implemented the plan. Burger King has remained adamant about not signing the deal because it buys tomatoes from repackers, not from growers, so it says it has no way to get money to the workers.

Reginald Brown, executive vice president of the growers exchange, contends the workers are fairly paid and that attorneys have warned the exchange against participating in the penny-per-pound proposal because it could ''open them up to lawsuits'' regarding anti-trust and labor laws. The exchange has threatened fines against its members for participating.

But Sanders produced a letter signed by 26 labor law professors who called the fear of litigation entirely ill-founded.''

And Sanders noted that McDonalds and Taco Bell's owner, Yum Brands, had been willing to pay the extra penny.

''You might want to reconsider the attorneys that you are currently consulting,'' he told Brown.

Though Brown called charges of slavery on the farms ''false and defamatory,'' a Collier County sheriff's deputy Charlie Frost told the committee ''human trafficking has surreptitiously found its way into our society.'' Frost said victims have been beaten and threatened and his investigations have been hindered by threats against victims' families.

Brown argued that workers are treated fairly, adding, the fact that thousands voluntarily return to our fields to pick tomatoes year after year, decade after decade, demonstrates that fact.''

But Lucas Benitez, co-founder of the Coalition of Immokalee Workers, said workers endure ''terrible exploitation'' and are paid about 45 cents ''a bucket'' -- a rate he said he not been significantly raised in 30 years.

To earn as much as the industry maintains, he said, a picker would have to fill a new bucket every two minutes.

''Realistically, it's an impossibility,'' he told the Senate Health, Education, Labor and Pensions Committee in Spanish, his words translated into English.

Sanders noted that growers have charged surcharges in the past -- to offset rising oil prices and ease the cost of phasing out the pesticide methyl bromide. The only difference is this time the surcharge would go to cover the cost of increased wages.

The challenge is that Florida tomato growers are already struggling with skyrocketing costs of everything from fuel to fertilizer that are cutting into profits, at the same time competition from Mexico is forcing prices down.

Burger King has already said that in light of the recent conflict with the Coalition of Immokalee Workers, the company is looking at contingency plans to buy outside of Immokalee and Florida. Losing business from Burger King and other fast-food industries would be a devastating blow to the industry.

But the plight of the tomato grower wasn't garnering much sympathy at the hearing.

Sen. Dick Durbin, D-Ill, said: "If Florida tomato growers can't live with workers being paid a decent wage, then I can live without tomatoes from Florida on my hamburgers.''

Watch video from the Senate hearing here.