Civil rights campaigner Jesse Jackson has warned that a disproportionate number of black pupils are being expelled from schools in the United States.

Last year, the Reverend Jackson led a protest against the two-year exclusion of six black high school students at Decatur in Illinois - arguing that such a penalty for a school brawl was excessive.

Speaking on the birthday of the assassinated civil rights' leader, Martin Luther King, Rev Jackson said that "Decatur is symbolic of a national crisis" and claimed that the dispute at the school was now one of the key civil rights issues in the United States.

According to Rev Jackson, while less than half of pupils in the Decatur school district were black, they represented 82% of the exclusions.

Where schools operated "zero tolerance" schemes, he said that it was black pupils who faced the harshest penalties.

Rev Jackson re-iterated his support for the campaign in Decatur against the exclusions, calling for an appeal against a judge's recent ruling in favour of the exclusions.

After a stand-off between school authorities and protestors led by Rev Jackson last year, the punishment against the teenagers was cut from a two-year exclusion to one year.

But despite a demonstration which forced the closure of schools in Decatur, the authorities refused to accept the call for a full re-instatement of the pupils.

The incident which sparked the exclusions had been a fight in the stands at a school football match in September, involving pupils from two high schools.