Deon Theron, vice-president of the Commercial Farmers Union, which represents the few white farmers left, also poured scorn on official predictions of large jumps in output of key crops such as maize and wheat in 2009.
He said the farm sector was being talked up in an attempt to persuade foreign donors to loosen their purse strings.
In many cases, forecasts were four times the reality, Theron said, since commercial farmers were being physically prevented from planting crops and banks were refusing to grant loans because they could not trust land deeds as collateral.
"It’s a joke. It’s ridiculous," Theron told Reuters in an interview in Johannesburg. "I find it incredible that those kind of figures could be put out. They’re not even close."
Zimbabwe, once the breakbasket of southern Africa, has recorded a consistent decline in its staple maize crop since 2000, when President Robert Mugabe’s government began seizing white-owned farms to resettle landless blacks.
Farms that escaped repossession have also suffered shortages of seed and fertiliser, making Zimbabwe reliant on imports and food aid since 2002. Aid groups have said up to 7 million people — more than half the population — may need food aid this year.
However, state media said this month the country would produce 1.2 million tonnes of maize this season, more than double last year’s crop.
Theron said the more likely figure was 400,000 tonnes — compared to a national requirement of 2.2 million.
"Agricultural production is in dire straits despite what the government is saying," said Theron.
The wheat crop was more likely to be 25,000 tonnes compared to 100,000 officially forecast and tobacco output was going to be a quarter of the 1.6 million tonnes projected.
Mugabe and political rival Morgan Tsvangirai joined a power-sharing administration in February and immediately started trying to raise the billions of dollars needed to rebuild an economy crippled by years of neglect and mismanagement.
Even though Tsvangirai said in March a new wave of farm invasions threatened $150 million of crops, Theron said Harare was glossing over the problems in the hope of convincing sceptical Western donors to get their cheque books out.
The farm invasions were, if anything, more frequent than before the joint government came to power, he said, leafing through a file of 60 incursions reported in April alone.
"It really is close to hoodwinking the international community into releasing funds by making them believe everything is fine on the agricultural front," said Theron, who has had three farms repossessed since 2000.
"We’re an agriculture-based economy. If agriculture does not recover, Zimbabwe will not recover," he said.