AMERICA’S most ambitious programme to give government vouchers to families to pay for private schooling has been thrown out by a judge who ruled the use of public money for private tuition unlawful.

The unexpected decision overturning Florida’s embryonic voucher scheme was based on state, not national, law, and has no effect in any other state.

But it comes just in time to transform the voucher question into a major issue in the presidential campaign, whose two likely contenders - Republican George W Bush and Democrat Al Gore - have diametrically opposite positions on it.

There’s also a personal element. Governor Bush’s brother, Jeb, is governor of Florida and has made the voucher scheme a centrepiece of his administration. George Bush has proposed using it as a national model.

Vice-president Gore, on the other hand, depends on the support of the nation’s teacher unions, which are zealously opposed to the idea.

“It’s a historic day for the nation, because all other states had their eyes on Florida and what Jeb Bush was trying to do here,” said Florida teachers’ union leader Pat Tornillo. “His brother wants to do the same thing with the nation. We stopped one brother, and we’re going to stop the other one.”

The Florida voucher programme, the only state-wide initiative of its kind in the nation, gives families in low-rated public school districts government credits they can use to send their children to parochal or private schools.

But Judge L. Ralph Smith ruled that diverting public money to private schools violates state law. The Florida constitution guarantees a “high-quality system of free public schools”, which Judge Smith said he interpreted to mean the state could support only public schools.

“Tax dollars may not be used to send the children of this state to private schools,” he wrote.

So far, only 52 children participate in the programme, which began this year on a limited basis. They will be allowed to finish the school year at the private schools they are attending, but the judge’s ruling bars the state from going ahead with plans to offer any vouchers next year. As many as an additional 75,000 students would have been eligible from the autumn.

Voucher proponents attacked the decision. “These children were trapped in failing schools and the private schools fulfil the state’s constitutional guarantee of a high-quality education,” said Clint Bolick, of the libertarian Institute for Justice.

They also pointed out that the voucher scheme was achieving another of its goals by forcing failing public schools to improve.

Following the withdrawal of students with vouchers, two Florida public schools responded by hiring more teachers, reducing class size, extending the school year and adding afternoon tutoring.

Governor Jeb Bush promised to appeal. Similar but more limited programmes in the states of Maine, Ohio, Pennsylvania and Vermont have also been quashed by state and federal courts.