Conservative Party members on Monday, 5 September, elected Liz Truss to be their next leader, effectively making her the next prime minister of the United Kingdom.
Truss will take over from Boris Johnson on Tuesday.
Following the declaration of results, Sunak urged all conservative mumbers to unite behind Truss.
The voting within the Tory party officially closed on 2 September.
Sunak had previously indicated that he would not serve in a government led by Truss.
The electoral contest for the top post commenced following PM Boris Johnson's resignation as the Conservative Party chief on 7 July.
'Must Work in Full Respect of Our Agreements': EU Chief to Liz Truss
The president of the European Union, Ursula von der Leyen, congratulates truss, saying "I look forward to a constructive relationship, in full respect of our agreements."
'Time to Scrap Energy Price Hike': Lib Dem Leader Calls for a General Election
Ed Davey, the Lib Dem leader, reacts to Liz Truss’s by urging for a general election.
"Under Liz Truss, we're set to see more of the same crisis and chaos as under Boris Johnson," Davey writes on Twitter.
'It's Right We Now Unite Behind The New PM': Rishi Sunak
After the declaration of results, Truss' contender, Rishi Sunak thanked Tory members for voting for him and urged conservative leaders to unite behind Truss.