The government's proscription of Palestine Action as a terror organisation is lawful, the Court of Appeal has ruled.

In one of the most significant rulings on national security in recent years, five of the most senior judges in the country overturned an earlier decision from the High Court that the ban had breached the right to protest and had been incorrectly taken by ministers.

Palestine Action has remained banned since that ruling in February to allow for further legal arguments and give the government time to consider an appeal.

But at a hearing on Monday, five Court of Appeal judges concluding the government's decision to proscribe the group "struck a fair balance".

In a statement, the group's co-founder Huda Ammori, who brought the original legal challenge against the Home Office, said she intended to appeal the ruling to the UK Supreme Court.

The proscription made it a criminal offence to belong to or support Palestine Action, punishable by up to 14 years in prison.

Thousands of people have been arrested at demonstrations in the months since the ban came into force in July last year.

Lady Chief Justice Baroness Carr and four other judges said that the government's policy on banning terrorism groups meant the home secretary had been legally entitled to decide the group should be proscribed.

She said it was not a "sustainable proposition" to portray it as a non-violent protest group.

"Palestine Action overly promotes unlawful violence that amounts to terrorism… It is not like the Suffragettes," she said.

She said the group had neither disowned nor condemned three incidents so far judged by ministers to amount to terrorism.

The threats posed by Palestine Action had been the most important factor in the lawful decision-making, Baroness Carr said, including how the group clandestinely organised and targeted lawful businesses.

That included defence firms involved in UK national defence and assisting Ukraine. The home secretary had been best placed to judge the impact of those threats, said the court.

Ammori said Palestine Action was "surprised by today's judgment" after judges in the High Court previously ruled the government "acted unlawfully in proscribing Palestine Action because of the significant interference with the rights to freedom of expression and peaceful assembly".

She added: "We will not stop fighting to overturn one of the most extreme attacks on free speech and the right to protest in modern British history."