But Christopher Mutsvangwa, a spokesperson for ruling Zanu-PF party, dismissed the report, saying that Amnesty International was resorting to baseless propaganda.
Mutsvangwa said the report didn't reflect ground realities, accusing Amnesty International of being a "sidekick of the British".
"Tsvangirai is the prime minister-designate ... events have moved on in Zimbabwe. Really, what is happening in Zimbabwe is not in the interests of the British who want regime change," he said.
Violence with impunity
|Amnesty says some of the victims were too badly injured to cultivate their land [AI]
The beatings allegedly took place in May, according to Amnesty, around the time when Tsvangirai decided to take part in the presidential run-off, after winning more votes than Mugabe in an inconclusive first round poll.
The opposition had accused the ruling Zanu-PF of unleashing a campaign of terror against its activists and sympathisers.
A man told Amnesty investigators that he was doused with petrol and then set alight. Another recalled being beaten until "his feet burst".
Amnesty said the perpetrators of the beatings usually were in the security forces, Mugabe's Zanu-PF party or were pro-Mugabe war veterans.
Mugabe and Tsvangirai's Movement for Democratic Change (MDC) agreed last month to share power, but talks have become bogged down over control of ministries.
Meanwhile, Zimbabweans are facing chronic shortages of meat, milk and other basic foods and commodities. The country is currently dependent on food handouts and malnutrition is on the rise.
Simeon Mawanza, Amnesty's Zimbabwe expert, said in a press release: "We are worried that human rights have not been at the centre of the negotiation process.
"While the parties continue to negotiate on political details, the most vulnerable Zimbabweans are at further risk of extreme hunger.
"Many Zimbabweans are now only surviving by eating wild fruit," he said.
The election-related violence had worsened the food crisis because many victims were farmers who were too badly injured to till their land during the coming rainy season, Amnesty said.
"If we think the food situation in Zimbabwe is bad now, just wait until the end of this year when half of the population is likely to need aid," Mawanza said.
Zimbabwe has an estimated population of 13 million.