Britain's grandiose Houses of Parliament are a universally recognized symbol associated with the legislature's reputation as the "mother of parliaments".

The home of Big Ben and the House of Commons' famous green benches is not just the setting for one of the world's oldest assemblies - it is also the venue for lobby groups hoping to promote their causes in an imposing setting.

One event planned for next week has attracted condemnation before it has even been held - because it is to support the leader of a recognized terrorist group.

On Monday, April 25, a U.K. opposition lawmaker will host the launch of a campaign for the release of Abdullah Öcalan.

Öcalan is the imprisoned head of the PKK, which has waged an armed conflict with Turkey for more than three decades, resulting in more than 40,000 deaths, and is listed as a terrorist organization by Turkey, the U.S. and EU as well as Britain itself.

He was arrested by Turkish forces in 1999 and sentenced to death for forming an armed gang under Article 125 of the Turkish Penal Code. The sentence was commuted to life imprisonment when the death penalty was abolished in 2004.

Turhan Özen, who leads the U.K. branch of the Union of European Turkish Democrats (UETD), a pro-Turkish lobby group, condemned the decision to use parliament as a venue in support of a recognized terrorist leader.

He told Anadolu Agency it was no different to Turkey proposing to host an event in support of other terror groups listed by the U.K.

"If Britain falls into the position of preferring the PKK over Turkey, it is making a big mistake," Ozen said.

"If Turkey were today to hold a campaign in its own parliament for an al-Qaeda representative or an ISIS [Daesh] representative, this would be no different to what Britain has done."

A poster promoting the event, which is organized by two of Britain's largest trade unions, argues calan be="" because="" he="" is="" must="" released="">

Encouraging terrorism

The event's legality is unclear. British lawmakers are certainly permitted to host lobby group events on the parliamentary estate and there are no restrictions on the content of the meetings.

Yet encouraging terrorism is a criminal offense under U.K. law that carries a prison sentence of up to seven years.

A spokesman for the Home Office told Anadolu Agency it was a matter for the police and prosecutors to decide whether the event would be considered an encouragement of terrorism.

However, Özen, the UETD leader, described the event as a grave error because it serves to legitimize the PKK.

"Countries and other entities that are bound by international agreements should not use terrorist organizations as tools because they eventually become a headache," he said.

"The terrorist organization known as the PKK may have done what you asked them to do in your fight against Daesh [in Syria], but once Russia became involved it transformed into an unknown entity.

"It is not an organization that you can do business with."

Monday's campaign launch is hosted by Labour Party lawmaker Kate Osamor, a close ally of the party's left-wing leader, Jeremy Corbyn.

Osamor represents Edmonton, a district of north London that is home to the largest number of Turkish speakers in the country.

It was her party that designated the PKK as a terrorist organization in 2001, under the government led by Tony Blair.

Sources in the Labour Party told Anadolu Agency this week that it had not changed its position on the PKK and the reasons behind the meeting were best discussed with the lawmaker herself.

Osamor did not return repeated requests for comment on whether she disagreed with the U.K. government's position that the PKK is a terrorist organization.