Tareque Rahman is the joint secretary-general of Khaleda's Bangladesh Nationalist Party (BNP), who's coalition government ended its five-year rule in October.
"Military-led security forces arrested Tareque Rahman from his home. He is now under their custody," a police officer told AFP news agency.
'Crime and corruption'
Power has been handed to a military-backed interim government until elections can be held later in the year.
The government, headed by Fakhruddin Ahmed, former head of the central bank, has vowed to clean up corruption before setting a date for the next election.
Polling was originally scheduled for January 22 but was postponed indefinitely in the wake of weeks of violence between BNP and opposition Awami League activists that killed 45 people and injured hundreds.
In the past few weeks, security forces have arrested more than 150 politicians, including more than a dozen former ministers, on charges of corruption.
They are being held in jail pending a full investigation of the charges against them.
Mainul Husein, a legal adviser to the interim government, said earlier this week that many more people were on a "wanted" list prepared by the law-enforcing agencies.