Foreign Secretary Tehmina Janjua summoned the British High Commissioner in Pakistan Thomas Drew on Friday over slogans being displayed on London cabs "that directly attack Pakistan's territorial integrity and sovereignty."
According to a statement released by the Foreign Office, "the high commissioner was informed that Pakistan, in line with the UN Charter, rejects actions and advertisements with malicious content that impinge on our sovereignty and territorial integrity."
It said that the "issue was also being raised with the Foreign and Commonwealth Office by our High Commissioner in London."
"Pakistan is aware of the intentions of such sinister and malicious campaigns, which should not be allowed on the soil of a friendly country," the FO statement read.
According to media reports, posters reading "Free Balochistan" slogans also appeared on vehicles in London.
A similar campaign in Geneva around the time of the UN General Assembly meeting had irked Pakistan earlier this year. "Any notion of 'Free Baluchistan' is a flagrant attack on [the] sovereignty and territorial integrity of Pakistan," Pakistan's permanent representative to UN had written to Swiss authorities.
He had linked the posters to the Balochistan Liberation Army (BLA), which, he said, is a "listed terrorist organisation under the laws of Pakistan and other countries, including the United Kingdom."
