CNN_ Activists from an animal rights group have vandalized the first official portrait of King Charles, currently on display in a London gallery.

Campaign group Animal Rising posted a video on its social media channels on Tuesday showing two activists using a paint roller to stick signs over the portrait of the monarch.

Members of the public have been free to visit the portrait of the monarch, which is on display at the Philip Mould gallery in central London until June 21.

The painting, the first official portrait of King Charles as monarch, raised eyebrows when it was unveiled earlier this year. Artist Jonathon Yeo depicted the king against a background of crimson red brush strokes, sparking mixed reactions.

Activists covered the king’s head with an image of the British cartoon character Wallace, from the “Wallace and Gromit” comedy series. A speech bubble sign was then also tacked onto the painting with the following caption: “No cheese Gromit, look at all of this cruelty on RSCPA farms.”

The action was designed to bring attention to a new report, released on Sunday by the group, which investigated 45 farms whose welfare standards are guaranteed by the Royal Society for the Prevention of Cruelty to Animals (RSPCA). The RSPCA’s Assured scheme promises that animals in protected farms are given more living space and are never kept in cages. Meat, fish and dairy products produced by these farms are marked with the RSCPA logo. Animal Rising described their findings as “damning,” alleging that they found “severe animal cruelty” at all farms visited.

Last month, King Charles became the royal patron of the RSPCA. In a statement provided to British newspaper The Telegraph, an Animal Rising activist explained, “With King Charles being such a big fan of ‘Wallace and Gromit,’ we couldn’t think of a better way to draw his attention to the horrific scenes on RSPCA Assured farms! Even though we hope this is amusing to His Majesty, we also call on him to seriously reconsider if he wants to be associated with the awful suffering across farms being endorsed by the RSPCA.”

(During a 2012 engagement at Clarence House for the late Queen Elizabeth’s Diamond Jubilee, Queen Camilla told a group of children of her husband that “Wallace and Gromit are his favorite people in the world.”)

Animal Rising describes itself as a non-violent organization campaigning for an “urgent transition to a sustainable and just plant-based food system.” It is also petitioning for the RSPCA’s Assured scheme, which it says covers up “cruelty on an industrial scale,” to be scrapped.

The RSPCA responded to Animal Rising’s claims in a statement provided to CNN on Tuesday, stating that “any concerns about welfare on RSPCA Assured certified farms are taken extremely seriously and RSPCA Assured is acting swiftly to look into these allegations.”

“We have responded openly and transparently to Animal Rising’s challenges to our farming work,” the statement continued. “While we understand that Animal Rising, like us, want the best for animals, their activity is a distraction and a challenge to the work we are all doing to create a better world for every animal.”

The organization also said it was “shocked” by the vandalism of the painting. “We welcome scrutiny of our work, but we cannot condone illegal activity of any kind,” their statement read.

According to Philip Mould, owner of the gallery where the portrait is on display, the painting sustained “no damage” since it was protected by a layer of Perspex. Mould told CNN the adhesive stickers used by the activists stayed on the portrait for “less than ten seconds.”

The activists left the premises after being asked to do so, Mould said, adding that the gallery has also filed a police report.

There are currently no plans to curtail the display of the painting, although staff will remain “on alert” after the incident, Mould said.