Arnold Tsunga said his client had been charged with publishing "false information" under the Public Order and Security Act, introduced ahead of presidential elections on March 9-11 won by President Robert Mugabe.
The poll was condemned as gravely flawed by the British and other Western governments. Critics say the security act is aimed at stifling political debate and criticism of Mugabe. If convicted, Thornycroft, a Zimbabwean citizen, faces a one year jail term or a fine of 20,000 Zimbabwean dollars ($360).
"The charges against her are without foundation and are the latest cynical act by a regime intent on crushing anyone who dares to question it," Alec Russell, the Telegraph's foreign editor, was quoted as saying on its web site.
Zimbabwe officials could not be reached for comment.
Thornycroft, 57, the Telegraph's Harare correspondent since July, was arrested by members of the Central Intelligence Organization in Chimanimani, 300 kilometers southeast of Harare.
She was investigating reports of a campaign of retribution against the opposition Movement for Democratic Change, whose leader, Morgan Tsvangirai, lost to Mugabe in the election.
"The CIO do not have policing responsibilities, so the arrest was irregular," Tsunga said. "She was surrendered to the police this morning and they decided to proceed with charges of contravening a section of the Public Order and Security Act," he added.
Local and foreign media organizations swiftly condemned the arrest and called for Thornycroft's release.
"It is becoming increasingly clear that Robert Mugabe intends to step up his campaign against the media and to restrict even further the flow of information to the people of Zimbabwe and the outside world," the Foreign Correspondents Association of Southern Africa said in a statement.
Zimbabwe was suspended from the Commonwealth for a year last week after election observers from the grouping of former British colonies accused Mugabe of electoral fraud.
The government has dismissed the accusations, saying Western powers want Mugabe ousted because he has seized white-owned farms for distribution to landless blacks.
A reporter for another British newspaper, The Independent's Basildon Peta, has said he fled Zimbabwe for South Africa last month after being briefly held under the security laws.
Zimbabwe's finance minister, Simba Makoni said Wednesday he was shuffling the country's 2002 budget to find money to feed hundreds of thousands of hungry Zimbabweans. Makoni said preliminary forecasts showed that the southern African nation would need to import more maize and other grains than was anticipated when the budget was presented in November.
"We are revising the 2002 budget in order to re-prioritize expenditure to create resources for food imports. My expectation is that by the middle of April, at the very latest, we would have finished that revision," he said.
Zimbabwe's economy is in its fourth straight year of recession with record high inflation and a severe shortage of foreign currency.
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