Litchfield made her international debut against India in December during the T20I series before impressing in her first appearance at ODI level against Pakistan in January with 154 runs in the three-match series.
Garth, the former Ireland allrounder who also made her first appearance for Australia in December, could also push for a Test debut as one of the pace options in a bowling attack that does not lack for options.
"Phoebe Litchfield has taken her game to the next level in the past 12 months, we view her as a long-term player for Australia and it's pleasing to reward her progress with selection in an Ashes squad."
The inclusion of Vlaeminck in the Australia A squad is significant with her having not played since early 2022 when she suffered another stress fracture of her foot during that season's Ashes.
"Tayla Vlaeminck is progressing in her rehabilitation and is working back towards full bowling fitness," Flegler said. "She is a highly regarded talent and is certainly part of our plans moving forward."
With the Australia A tour overlapping the first part of the Ashes, there is a chance for players to cross over if form or injuries require reinforcements with the main group. The A tour will include three T20s and three one-day games between June 21 and July 2.
"It's hugely beneficial to have an Australia A component to the tour and provide an opportunity for our developing players to test themselves in conditions they may not experience in Australia," Flegler said.
"The nature of concurrent tours also offers flexibility and allows players to be available for and cross over into both squads, whether it be from a preparation perspective or to provide an opportunity at international level.
Australia Ashes squad: Meg Lanning (capt), Darcie Brown, Ashleigh Gardner, Kim Garth, Grace Harris, Alyssa Healy, Jess Jonassen, Alana King, Phoebe Litchfield, Tahlia McGrath, Beth Mooney, Ellyse Perry, Megan Schutt, Annabel Sutherland, Georgia Wareham
Australia A squad: Maitlan Brown, Lauren Cheatle, Maddy Darke, Heather Graham, Nicole Faltum, Tess Flintoff, Charli Knott, Kate Peterson, Courtney Sippel, Tayla Vlaeminck, Courtney Webb, Amanda-Jade Wellington, Tahlia Wilson