British Prime Minister Boris Johnson. Photo: VCG

London's High Court on Friday rejected a legal challenge against British Prime Minister Boris Johnson's suspension of parliament before Brexit, but said it could still be taken to the Supreme Court for a final appeal.

Johnson announced at the end of August that he would suspend parliament from mid-­September to mid-October, just before Britain is due to leave the EU on October 31, so the government could announce a new legislative program.

That prompted campaigner Gina Miller, who defeated the government over another Brexit issue two years ago, to bring a legal challenge. 

She was later joined by former prime minister John Major and opposition political parties.

Miller said that parliament should be sitting during such a crucial time for Britain's democracy, and she would not give up the fight.

"The Supreme Court has penciled in September 17 for the appeal hearing... My legal team and I will not give up the fight for democracy."

Miller's lawyer David Pannick argued that comments from Johnson showed an important part of his reasoning for the prorogation was that parliament might say or do something that impeded the government's Brexit plans.