Democratic Alliance leader Mmusi Maine was deported from Zambia because he intended pressurising the courts to release Hakainde Hichilema, the country's High Commissioner Emmanuel Mwamba said on Friday.
Mwamba claimed that Maimane's comments about Hichilema, who is on trial for treason, were problematic as he intended to mobilise Zambian opposition parties.
"DA leader Mmusi Maimane was turned away from Zambia as his presence was going to undermine the sanctity, integrity and independence of the judiciary," Mwamba said.
Maimane was refused entry into Zambia on Thursday evening after he landed at Lusaka International Airport to support Hichilema, leader of the opposition United Party for National Development, who goes on trial on Friday.
The maximum sentence for treason in Zambia is death.
Maimane said that, as he landed at the airport, police and immigration security were already waiting for him.
"On arrival, members of the Zambian police boarded the aircraft and aggressively confronted me and the delegation I was travelling with.
"I was not allowed off the aircraft and was told I was not welcome in Zambia. When I demanded reasons for being refused entry, I was told that the authorities are not required to furnish me with a reason.
"Within an hour of arrival, I was deported back to South Africa."
'Disregard of the rule of law'
Maimane said that Hichilema was violently arrested over six weeks ago for allegedly attempting to block Zambian President Edgar Lungu's motorcade.
"The violent nature of his arrest, and the inhumane treatment that Hichilema has received in detention, confirms the political motives behind these charges.
"I have no doubt these charges were manufactured by the Zambian government to intimidate those who are opposed to its oppressive rule, which is an abuse of power and a serious disregard of the rule of law."
Mwamba claimed that Maimane had not been truthful in his statements about Hichilema and that he had dramatized what happened to him on Thursday evening.
A group of DA supporters and a group of Zambian nationals supporting Lungu were outside the embassy on Friday as Maimane met with Mwamba.
The group supporting Lungu chanted "Zuma", in reference to President Jacob Zuma, and booed Maimane as he entered and left the embassy.
After the meeting, Maimane said he wanted the full reasons for his deportation, and he requested the high commission to allow him to attend the next court appearance.