Clark said Harry Bloy has taken responsibility for his actions by resigning, and did nothing illegal.
She said Bloy, first elected in 2001, told her prior to his resignation that he would not be seeking re-election in the May 2013 provincial election.
"It was improper and it was an error in judgment and Harry Bloy is an honourable person and he has stepped up and he's done the right thing in this case," Clark told reporters in Victoria on Thursday.
Bloy, who was minister of state for multiculturalism, was demoted last fall as social development minister.
That was after social groups and the Opposition New Democrats mounted considerable attacks on the ministry's underfunding of Crown agency Community Living B.C., which funds and operates programs for adults living with disabilities.
Shortly after Bloy was replaced by current Social Development Minister Stephanie Cadieux, who announced two reviews of CLBC, the government increased the agency's funding by $40 million in January.
Bloy was not in the legislature Thursday when his resignation was announced with a statement from Bloy, which said he had accepted responsibility for sharing an email with a third party.
Clark confirmed the email from a Vancouver newspaper reporter was to the Ministry of Advanced Education, asking about Eminata Group founder Peter Chung.
Chung, who has donated $14,000 to the B.C. Liberals in the past, founded the Eminata Group, which operates private colleges and other training institutions.
"It has been my honour to serve in cabinet for the last year but I felt it important to accept responsibility for my actions in regard to sharing an email with a third party," Bloy said in his resignation statement.
"It was my decision and I accept that."
Clark said cabinet ministers often share emails between each other, but Bloy should not have sent the Advanced Education Ministry email to the Eminata Group and Chung.
"He shouldn't have received the document," she said. "It was inappropriate and the minister has resigned. There's no ifs ands or buts about it, it was inappropriate."
Bloy's resignation saw the New Democrats calling for a second resignation, pointing to Advanced Education Minister Naomi Yamamoto, who's ministry received the original email and passed it on to Bloy.
Yamamoto said she wasn't quitting and denied she or her ministry were guilty of wrongdoing in letting Bloy see the email.
"No," she said. "I haven't done anything wrong. My staff haven't done anything wrong. I have confidence that other ministers, if we share information with them, keep that confidential. I have no reason to expect Mr. Bloy would do otherwise."
NDP advanced education critic Michelle Mungall said Yamamoto should resign because her staff allowed Bloy to leak the email to Chung.
She questioned why Bloy received the email.
"Why Harry Bloy?" said Mungall. "What was the purpose of giving it to him? Why did he give it to Eminata? This question hasn't been answered."
Yamamoto said Bloy received the email because as multiculturalism minister he regularly deals with issues involving ethnic communities and education facilities similar to the Eminata Group.