Britain's opposition Labour Party said on Tuesday that Home Secretary Sajid Javid had to provide evidence to justify his decision to widen a ban on the Lebanon-based Shiite terror movement Hezbollah.
Britain said on Monday it plans to ban all wings of Hezbollah due to its destabilizing influence in the Middle East, classing the movement as a terrorist organization.
"The Home Secretary must therefore now demonstrate that this decision was taken in an objective and impartial way, and driven by clear and new evidence, not by his leadership ambitions," a Labour spokesman said.
Asked about the comments, British Prime Minister Theresa May's spokesman said it was for Labour to explain their decision.
"Hezbollah itself has publicly denied a distinction between its military and political wings. The group in its entirety is assessed to be concerned in terrorism," the spokesman said. "The links between the senior leaders of Hezbollah's political and military wings as well as the group's destabilizing role in the region mean that the distinction between the two wings is now untenable."
The British ban, which will come into force on Friday subject to parliament's approval, means anyone who is a member of Hezbollah or invites support will be committing a criminal offense with a potential sentence of up to 10 years in jail.
Labour leader Jeremy Corbyn has previously been criticized for his approach to Hezbollah, whose members he once termed "friends." The remark is regularly seized upon by opponents for criticism.
"What do we see from his Labour Party? Hamas and Hezbollah friends, Israel and the United States enemies," May said just last week.
Labour under Corbyn's leadership has also been plagued with accusations of anti-Semitism, both by leading members of the party and by its failure to tackle the growing phenomenon. Last week, seven Labour members of parliament broke away from the party to form an independent bloc, with many of them citing anti-Semitism as factor in their decision.
Hezbollah was already considered a terrorist organization by multiple countries, including Israel, the US and members of the Arab League.
In 2013, the European Union placed the military wing of Lebanese party Hezbollah on its terror list, and London had proscribed the group's external security unit and its military wing in 2001 and 2008 respectively. Now, the UK plans to add the political arm to that list too.
"Hezbollah is continuing in its attempts to destabilize the fragile situation in the Middle East, and we are no longer able to distinguish between their already banned military wing and the political party," Javid said Monday. "Because of this, I have taken the decision to proscribe the group in its entirety."
The ban is a response to an Israeli request to the UN Security Council, filed earlier this month. Israeli representatives voiced their concerns over Hezbollah's growing power within Lebanon and the establishment of extensive terror infrastructures, and also raised the need to prevent further Iranian entrenchment in Syria.
Late last year, Israel launched a military operation to locate and destroy attack tunnels dug by Hezbollah across the Israel-Lebanon border.