Blogger Leong Sze Hian, who is being sued by Prime Minister Lee Hsien Loong for defamation, is appealing against the High Court's decision in March to dismiss his counterclaim.

In Facebook posts yesterday, Mr Leong said he had filed his submission to the Court of Appeal, and also shared images of the 12-page document. The hearing dates for his appeal would likely be some time in September, he added.

In his countersuit, Mr Leong had contended that PM Lee's libel suit was an abuse of court process.

In a written judgment dismissing Mr Leong's countersuit in March, Justice Aedit Abdullah found that it did not have a "reasonable cause of action", as the legal basis it was premised on did not exist.

In allowing PM Lee's application to strike out Mr Leong's counterclaim, Justice Aedit pointed to an earlier judgment by a five-judge Court of Appeal, which ruled that the abuse of court process is not recognised in Singapore law.

But in his submissions yesterday, Mr Leong, represented by lawyer Lim Tean of Carson Law Chambers, argued that an exception should be made. "The tort of abuse of process should be available in limited circumstances where a need to restrain abuse of a public function arises," said the submissions, adding this is "especially required in situations where there is interference with freedom of expression".

Among other arguments, Mr Leong contended that if the abuse of process argument is used as a defence to PM Lee's defamation claim during the trial, it would be "unjust if there was no remedy" for a defendant in circumstances in which the court had found abuse.

The libel suit began last November when PM Lee commenced legal action against Mr Leong, after the blogger shared on Facebook an article alleging PM Lee had helped to launder money from the 1Malaysia Development Berhad fund.

Mr Leong responded a month later by filing his defence and a countersuit. In January, he also applied to strike out PM Lee's claim against him. Both applications were dismissed by the High Court.