BNP acting Chairperson Tarique Rahman has sent a legal notice to State Minister for Foreign Affairs M Shahriar Alam.
In the notice, he sought proof within 10 days over the allegation that he gave up his Bangladeshi nationality by submitting his passport.
Barrister Kaiser Kamal served the notice on behalf of Tarique Rahman on Monday saying that appropriate legal action would be taken against Shahriar Alam unless he is able to prove the allegation and withdraw his remark.
Earlier on April 22, State Minister for Foreign Affairs M Shahriar Alam said Tarique Rahman surrendered his nationality by handing over his Bangladesh passport.
"How does he play the role of BNP's acting chairman? He rejected Bangladesh nationality by surrendering his green passport," he said.
The state minister made the remarks while addressing a reception hosted by the UK Awami League in honour of Prime Minister Sheikh Hasina in London.
Tarique Rahman has been living in London for the last nine years.