Among recent projections highlighted by a House of Commons spokesperson includes a swastika by the campaign network Awaaz to protest against the Prime Minister's visit last November with the message "Modi Not Welcome".
"Unauthorised projections break planning permission regulations. They also dilute the impact of a marketing technique that Parliament reserves for moments of national significance," Lee Bridges, Commons' director of external communications, told advertising magazine 'Campaign' last week.
"These buildings are not free billboards - proposals to project commercial campaigns that are not in the national interest will not be granted permission. The council can pursue incidents where a projection has been made without its permission," he warned.
Awaaz had projected a sword-wielding Modi on to the Gothic Parliament building as part of a wider "Modi Not Welcome" protest against his visit to London last year.
Bridges added: "The Houses of Parliament are recognised around the world as a symbol of the UK and a must-visit for tourists. As an iconic sight, it is perhaps unsurprising that Parliament - and, in particular, Big Ben (the Elizabeth Tower) - has become the backdrop for guerrilla marketing projections.
"However, as a much-loved, Grade I-listed public building, it is important to protect Parliament's symbolic status. Having commercial messaging beamed on to it compromises this status, which is why there are planning laws requiring permissions before any projection is allowed."
He stressed that to legally project on to the Houses of Parliament, people need permission from both the Speaker of the House of Commons and the planning department of Westminster City Council.
"The Houses of Parliament, famed for their stunning Gothic architecture, are part of an Unesco World Heritage Site and need to be enjoyed as such," he said.
Besides the protest by Awaaz, other unauthorised projections included a monkey by British tea firm PG Tips last month to mark Lunar New Year, which is the Year of the Monkey as well as an advert for a weight loss brand.
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