Chowdhury, who was known to be close to the party’s top leadership, told on Thursday that he has written to party chief Khaleda Zia about his decision.
His resignation was sent to Acting Secretary General Mirza Fakhrul Islam on Wednesday.
“I was wounded during the 1971 Liberation War and am not physically fit anymore for politics. That’s why I decided to step down and give up all party positions with immediate effect,” he said.
A gallantry award winning Freedom Fighter, Chowdhury was an army lieutenant in 1971. He was deputed to the foreign ministry after the Liberation War.
He served as the foreign secretary between 2001 and 2005 during the BNP-Jamaat alliance government.
In 2008, he joined the BNP after being the Bangladesh envoy in the US for two years.
Chowdhury was made a vice chairman after the BNP’s national convention in 2009.
He was arrested in early 2015 during the BNP-led alliance’s non-stop blockade and later released on bail.
The former diplomat told that he had eye and prostrate problems. “I need to go abroad for treatment. I have applied for a renewal of my passport and will leave as soon as I get it.”