Carrie Symonds, 31, was seen laughing and smiling in a yellow dress as she attended an event sat by her 55-year-old boyfriend’s side.
The blonde attended the reception at Downing Street at the Prime Minister’s other half.
Downing Street posted the images, but did not mention the appearance on the Prime Minister’s girlfriend.
It wrote: “The Prime Minister was joined by six hospices, where he shared with them how grateful he was for the difficult but vital and caring work they do.”
Carrie wore the Whistles Ilana Check Shirt Dress in Yellow/Multi, which costs £159.
Whistles said of the gown: “Decorated with a charming check pattern, this Ilana shirt dress from Whistles is sure to serve you well as a fetching warm-weather piece.
“Equipped with front button fastening, this dress is fitted towards the waist to ensure a form-flattering silhouette.”
Carrie has been compared to Kate Middleton before after wearing very similar looks. Is Carrie Symonds copying Kate Middleton?
Kate wore a very similar dress to Carrie’s to a recent polo game. This was a low key look for the Duchess, although she likely knew photographers would be taking pictures.
This dress was a coral hue, but Kate has worn pale pink and hot pink alike.
Carrie has also been seen wearing a very similar red print midi dress with long sleeves to one Kate owns.
Not everyone thought it was appropriate for Carrie to attend the Downing Street event.
One Twitter user wrote: “Why is his girlfriend there? Why is she at an official government event, don’t remember anyone voting her into an elected position.”
“Is that the PM with his niece?” another joked, clearly making a point of the huge age gap between the couple of 24 years.
Caroline Wolf, who is a personal stylist for influential businesswomen and has styled members of international royal families told Express.co.uk: “With her choice of a Ghost dress for Boris Johnson’s recent arrival at No. 10 Downing Street, Carrie Symonds has shown without doubt that she is confident in her own personal style and is not someone to copy Kate Middleton or Melania Trump.”
However, she did state that Carrie is likely to have made some deliberate choices when picking this dress.
“The Ghost midi dress sent out several key messages,” Catherine explained.
Carrie seemed to be aware of her position as a girlfriend of a Prime Minister, and dressed accordingly.
“It wasn’t a statement or presidential dress such as a wife might wear, but one from the British High Street, costing an affordable £120.”