Zimbabwe's opposition MDC Alliance is trying to raise $129,000 (£100,000) to pay legal fees after the country's highest court dismissed its application to annul President Emmerson Mnangagwa's victory in heavily disputed elections in July.
The Constitutional Court's ruling was "against overwhelming public opinion", and "worse still, it carried a punitive condition requiring [MDC Alliance candidate] Nelson Chamisa to foot the legal costs of everyone involved", its fund-raising page says.
More than £9,000 had been raised in the first day.
Mr Chamisa boycotted Mr Mnangagwa's inauguration in the capital, Harare, on Sunday.
He maintains that the result was rigged to give Mr Mnangagwa outright victory.
Ousted President Robert Mugabe and his wife Grace were also absent from the inauguration. However, their daughter, Bona, and her husband, Simba Chikore, were present.
Mr Mugabe had backed Mr Chamisa in the election, despite the fact that he once saw him as an "enemy" and a "puppet" of the West.
In his inauguration speech, Mr Mnangagwa read out a letter from Mr Mugabe amid cheers from the crowd, the state-linked Herald newspaper reported.
“Your Excellency, thank you for your invitation to me and my wife to attend the inauguration ceremony. My wife is not well in Singapore and also I am not well. So I am sending my daughter and her husband to represent us. Hearty Congratulations,” the letter said.
The military forced Mr Mugabe, 94, to resign in November, opening the way for Mr Mnangagwa to take power.