The [anti-plunder] law is constitutional, no question about it

Supreme court spokesman Ismael Khan

A majority of judges ruled the anti-plunder law, under which Mr Estrada is charged, is constitutional.

Mr Estrada, who was ousted from power in January amid popular protests, is charged with plundering $80m in state funds during his 30 months in office.

If convicted, he could face life imprisonment or the death penalty.

His lawyers had argued the anti-plunder law was vague. They said it denied Mr Estrada his constitutional right to know clearly what the charges against him were, and to mount a proper defence.

Majority decision

Ten judges voted against Mr Estrada, four in favour and one abstained.

Mr Estrada was ousted in January and arrested in April

Supreme court spokesman Ismael Khan said: "The Supreme Court said the law is constitutional, no question about it."

A lawyer for Mr Estrada said his legal team would examine the decision closely before deciding what further course of action to take.

"There may be something in the decision that's favourable to us, like the amount of evidence that would be required for a conviction," Raymond Fortun told the Associated Press news agency.

But the government's chief prosecutor, Ombudsman Aniano Desierto, said the decision left no doubt and the trial would now proceed.

The trial in the anti-corruption Sandiganbayan court has been overshadowed in the past few weeks by a public row between judges and allegations of bribe-taking made against Mr Desierto.