Venezuela's congress has sworn in three opposition lawmakers in violation of a Supreme Court ruling that is likely to further inflame the country's political divisions.

Electoral authorities certified the victory of the indigenous lawmakers as part of the opposition's landslide victory in December elections. But they were denied their seats after government allies alleged electoral irregularities in the Amazon region and the high court ruled that any legislation passed with the three lawmakers voting would be nullified.

The court's decision denied the opposition a two-thirds super majority that would have allowed it to dramatically challenge President Nicolas Maduro's socialist rule.

The government-stacked Supreme Court has shot down almost every piece of legislation passed by congress. But on Thursday opposition leaders vowed to ignore future court rulings that they consider unconstitutional.