Hancock said Zatuliveter was a "conscientious worker" and denied she has done anything improper, reports Sky News.
"I have no reason to believe she did anything but act honourably all the time she was working for me," he said.
"She assures me she has yet to see any evidence presented against her," Hancock added.
Zatuliveter, 25, was taken into custody on Thursday and is awaiting deportation. The Sunday Times first reported that MI5 believed the woman was secretly working for Moscow's intelligence service as a "sleeper" agent.
A source told The Sunday Times, "Her presence here is not considered to be conducive to national security. There was unhappiness about what she could have access to. The intention is to show her the door."
Hancock, a member of the House of Commons defence select committee, dismissed the spying allegations against her.
"I think is absolutely ludicrous. I have never had any inclination at all that Katia was anything other than a very conscientious worker. She had access to papers but none of them were in any way not public documents, in the sense that they were available at sometime, somewhere," he said.
"So, I do not see what anyone would have benefited from that. She is determined to fight her corner and she genuinely believes - and I back her 100 percent - that she has nothing to hide and she has done nothing wrong," he added.
The Lib Dem MP for Portsmouth South said, "I am shocked and surprised because when she was first interviewed back in August she had has regularly assisted the authorities since then. She could have left the country at any time, but she has always maintained that she has done nothing wrong."
"I have supported that, if you have done nothing wrong and there is no evidence to the contrary, then you have a perfect right to go on to with your life."