Mugabe's comments came after the opposition Movement for Democratic Change (MDC) made huge gains in the June 24-25 parliamentary elections. The MDC won 57 of 120 contested seats to claim a much stronger presence in the 150-seat parliament than many had expected. The previous parliament included only three opposition delegates.
But the president said he was not surprised by the results.
"I wasn't that much surprised. The results might have gone beyond our calculations, but ... the people would naturally vote against the party, against the government because of the hardships," he said.
Zimbabwe had one of Africa's strongest economies when it achieved independence from Britain in 1980. In recent years it has struggled with high unemployment, soaring inflation and crippling fuel and hard currency shortages.
White farms occupied by war veterans
Mugabe also said MDC is sponsored by Britain and white farmers opposed to the land-grab policy that is backed by the president.
Hundreds of white-owned farms have been invaded this year in attacks led by the Zimbabwe National Liberation War Veterans Association. The group is headed by Chenjerai Hunzvi, who is awaiting prosecution on medical fraud charges.
Mugabe is firmly behind the veterans -- and has said he will support more farm seizures. He dismisses objections voiced by Britain and representatives of white landowners.
Mugabe will not deal with opposition party
"This is our land, these are our policies. (They) must accept them. If they don't, let them be gone," he said.
He also repeated his pledge not to deal with the MDC or hand it a role in government until it can prove it is not financed by the white farmers and backed by London.
"At the moment we tend to feel that they have been put together ... by others with ulterior motives.
"We believe that the farmers had a lot to do, financing them, that Britain is behind it all," he said.
Britain urged Mugabe's ruling ZANU-PF party on Tuesday to accept that voters had called for change and said it should work together with the opposition.
CNN's Johannesburg Bureau Chief Charlayne Hunter-Gault contributed to this report