Tin Oo, 83-year-old vice-chairman of the National League for Democracy (NLD), was freed after more than six years in detention and said he would resume political activities even though he was warned to desist.
Tin Oo invited reporters into his residence after the departure of a police officer.
He read out the order lifting the house arrest on me and the order also said I should not be engaged in political activities or create political unrest, Tin Oo said.
But he added: I'll continue my political activities in my capacity as the vice-chairman of the NLD party.
Suu Kyi is also under house arrest and a minister said last month that she would be released when her latest period of detention ended in November. That would probably be too late for her to play any part in elections scheduled for this year.
She has appealed against her sentence for security breaches but the minister's comments suggested the appeal would fail.
Tin Oo, a former army general, was jailed in 2003 for breaking a draconian anti-subversion law and was transferred to house detention in 2004.
The NLD, which won elections in 1990 by a landslide but was never allowed to rule by the military, has yet to decide whether it will run in the polls due sometime this year.It is waiting for the junta to unveil election laws governing who can take part and is demanding that 2,100 political prisoners be freed, including Nobel Peace Prize winner Suu Kyi.
The NLD has threatened to boycott the election, the first in 20 years, because it believes the constitution passed in 2008 grants too much power to the military, which has ruled the former British colony for almost half a century.
In comments published in Friday's newspapers, reclusive junta supremo Than Shwe, who has made few public comments about the polls, said a free and fair election would take place soon.
The regime has yet to set a date for the election, which critics say will create a weak parliament powerless to counter the heavy influence of the military and its stooges.
(Writing by Martin Petty; Editing by Alan Raybould)