Ms Dorries, a supporter of Mr Sunak’s leadership rival Liz Truss, pointed to reports the millionaire former chancellor has been pictured wearing a £3,500 suit and £490 Prada shoes.
She said foreign secretary Ms Truss is more likely to be seen in a pair of £4.50 earrings from high street chain Claire’s.
Her comments provoked a backlash from parliamentary colleagues.
It is the latest sign of the bitter, highly personal nature of the Tory leadership battle.
Mr Sunak was seen wearing a Henry Herbert suit – worth a reported £3,500 – ahead of the vote that saw him and Ms Truss selected by Tory MPs as the final two candidates to be the next Conservative Party leader and prime minister.
His choice of Prada shoes on a visit to a construction site in Redcar also caught Ms Dorries’ attention.
The culture secretary said Ms Truss “will be travelling the country wearing her earrings which cost circa £4.50 from Claire (sic) Accessories.
“Meanwhile… Rishi visits Teeside (sic) in Prada shoes worth £450 and sported £3,500 bespoke suit as he prepared for crunch leadership vote.”
Guildford MP Angela Richardson, a supporter of Mr Sunak, shot back: “FFS (for f***’s sake) Nadine! Muted.”
Cabinet Office minister Johnny Mercer said the leadership contest was embarrassing.
He warned “on current trajectory” the party would be out of power in two years’ time.
“The puerile nature of this leadership contest is embarrassing,” he said. “Time to raise the standards.”