The campaign was created by The Story Lab and The Outfit, and the deal brokered by Carat and Channel 4. The films continue the "Pyjama Mama" theme introduced by Mother in its recent ad for the car brand.
Both Hynes and Phillips made their names writing and starring in Channel 4 comedies of the late 90s: Spaced and Smack the Pony respectively.
Hynes is possibly best known today for playing ditsy PR boss Siobhan Sharpe in BBC sitcoms Twenty Twelve and W1A, while Phillips’ roles include Shazza, in all three Bridget Jones films.
Kate Lunt, campaign lead at Carat, said: "It was important for us to think bravely and put our female target audience first in the campaign as they play a hugely influential role in car purchase decisions.
"Channel 4 was the perfect partner to bring the campaign’s energy to life and by using comedic talent we created alongside The Outfit and Channel 4, something truly entertaining for mums that they can completely relate to."
Angus Mitchell, agency principal at Channel 4, added, "We are really proud of this bespoke campaign created with Channel 4 alumni Jessica and Sally, together with Vauxhall Motors.
"The ads present an honest and fun reflection of being a mum which makes them relatable for our viewers and build perfectly of Vauxhall Motors’ Pyjama Mamas launch campaign."