The parliamentary vote was won by Mr Tsvangirai's Movement for Democratic Change (MDC) party.
But the election commission is conducting a recount in 23 of 210 constituencies that could overturn that result which saw President Robert Mugabe's Zanu-PF lose its majority for the first time since independence in 1980.
The MDC's secretary general, Tendai Biti, said the party would not accept any recount in respect of parliamentary seats "because ballot boxes have been stuffed".
"Those ballot boxes have become pregnant and reproduced," he said.
The government has dismissed the accusation of tampering.
It is thought the recount may also lead to a run-off vote in the presidential poll.
Mr Tsvangirai, who is adamant he won the election outright, has fled the country, saying he fears for his life.
His party has said Mr Tsvangirai will not contest a run-off unless certain conditions are met - such as a secure environment, with thorough international monitoring.
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