Former presidential candidate, granted political asylum in Britain, is worried about the safety of his family.
Andrei Sannikov believes the autocratic government Alexander Lukashenko could eventually fall, he said on Thursday to the world's largest news agencies "Reuters".
A former deputy foreign minister, Sannikov, 58, moved to Britain in August after being released from prison where he said officials tried to push him to kill himself.
In his first interview since coming to Britain, the soft-spoken and bearded Sannikov said his wife, Irina Khalip, was unable to leave the capital Minsk and join him in Britain because of restrictions imposed on her by the government.
"The most important thing for me now is my family and the safety of my family," Sannikov added, saying he had taken the decision to leave because it was impossible for him to stay in the country any longer.
Sannikov ran against the veteran Belarus leader in the 2010 presidential poll which Western observers said was fraudulent, and was sentenced to five years in jail last year for taking part in a protest against Lukashenko's re-election.
His wife has herself been given a suspended sentence over the protests and is barred from leaving Belarus.
"She has to be at home every day and police are watching her. Sometimes they deliberately visit in the middle of the night even though there is a small child."
Lukashenko has run Belarus since 1994, tolerating little dissent and maintaining a welfare state thanks largely to Russian economic support.
His crackdown on the opposition movement after the 2010 election prompted the European Union to impose travel bans and asset freezes on the president and several other Belarussian officials and businessmen.
"It's not a functioning system," Sannikov said. "At the moment (state) resources are aimed at crushing all forms of protest. Through all these years the authorities have only confirmed they are not capable of reform."
Asked if Belarus could one day witness the kind of revolutionary change that has swept the Arab world since early 2011, Sannikov said: "Theoretically, everything is possible".
He added he was prepared to step in to fill any ensuing political void and lead his homeland towards closer ties with Europe but said that Lukashenko's grip on power was very strong.
"I do want to go back to the country as soon as possible. If I am useful to the country then of course I would accept certain proposals," Sannikov said.
"But it's too early to say that ... This situation (exile) is not normal for me, it's a hideous situation. Of course I want to go back to the country, to a free country."
Lukashenko's system depends on financial backing from Russia, its former Soviet overlord which provides Belarus with cheap energy and other benefits, and has so far shown little sign of growing grassroots dissent.
"The game is always the same," Sannikov said. "(Lukashenko) needs money. He wants to retain authority, and to retain authority, he wants to retain this obsolete economic model.
"His aggressive behaviour against the West helps him secure Russian cash, and he is right. When Russia starts making economic demands he softens his rhetoric against the West. This game has now become very cynical."