The dress attracted attention after eagle-eyed viewers noted that it was the same garment worn by Vivienne Rook, the right-wing prime minister played by Thompson, in BBC drama series Years and Years.
Commentators made the comparison after Vivienne’s right-wing policies were compared with those of the prime minister.
Now, the designer of the garment has described it as a uniform for “powerhouse women”.
Head of design at Karen Millen, Bonnie Godsil, told The Independent: “We use premium fabrics and craftsmanship to deliver accessible luxury for the Karen Millen women. The “Forever” dress is a prime example of this – with it being a bestseller for us for seven years, it is the epitome of power dressing.
Noting that the style originally began as a sleeved midi-pencil shape silhouette, Godsil added that the Forever range now extends to A-line to pleated, sleeveless to short pencil versions. “Our powerhouse women know they can come to us to invest in well-tailored pieces that never go out of style, and last forever,” she said.
Godsil said that the “sharp V necklines” have “universally broad appeal, because they flatter all bust sizes. Ours work so well because the neck edge is raised up the side and the back of the neck, so the v shape is very slim and long, elongating both the neck, and the length of the shoulder.
“The notch collar detail brings an additional sharpness to the dress , drawing attention to the face and making the dress instantly recognisable.”
The “Forever” dress was first launched in 2015 and has been a consistent bestseller year-on-year, and comes in sizes 6-26.
Like many female politicians, Truss has been subject to scrutiny over her wardrobe, but some have stated that commentators should focus on her actions, not her clothing.
“Do we really need to over analyse the comparison between the red dress Liz Truss is wearing to Emma Thompson’s demonic character in the BBC series Years and Years to realise we are living in twisted times?” wrote domestic violence campaigner David Challen.
“Can we slate Truss for her policies and not what she’s wearing please? Let’s not give Truss and Tories ammunition. They need to save that for themselves.”