The Philippine government has lost a decades-old legal effort to seize millions of dollars from the estate of former dictator Ferdinand Marcos, a court said Friday, accusing state prosecutors of failing to produce admissible evidence.

Lawyers had submitted "defective" evidence consisting mostly of poor-quality photocopies, some of which were no longer readable, Justice Alex Quiroz of a special anti-graft court said in a release of the October 14 decision.

The ruling was another blow to efforts to recover the late dictator's alleged ill-gotten wealth after the court also ruled in favour of Marcos's estate on another multi-million-dollar case in September.

After a bloodless "people power" revolt chased Marcos into US exile in 1986, the Philippines launched a global bid to recover at least $10 billion in assets that the Marcoses and their cronies acquired using funds allegedly stolen from state coffers over his 20-year rule.

It has recovered 172.6 billion pesos ($3.4 billion at current market rates) so far, according to the government agency tasked with tracking down the assets.

A lawyer for the Marcos family declined to comment, while President Rodrigo Duterte's spokesman Salvador Panelo said his government does not interfere with the courts.

The office of the Ombudsman that handles hidden wealth cases did not respond to an AFP request for comment.

About a dozen forfeiture cases against the Marcoses have yet to be resolved.

The heirs returned to the Philippines after the patriarch died in exile in Hawaii in 1989, later getting themselves elected to congressional seats and local posts.

Rodrigo Duterte's election in 2016 cemented their comeback as the government gave the ex-president's remains a hero's burial and publicly floated the idea of winding down the hunt for his hidden wealth.

"We all know that the Duterte government is very hospitable, to say the least, to the Marcoses," said Bonifacio Ilagan, one of thousands imprisoned during the dictator's rule and now spokesman of a citizens coalition seeking to prevent the Marcoses from regaining the Philippine presidency.

In a rare legal setback last year, a court sentenced Imelda Marcos to at least six years in prison for each of the seven charges that the family funnelled roughly $200 million of embezzled funds through Swiss foundations decades ago.

However, she remains free on bail after filing an appeal with the Supreme Court.