Labour leader Keir Starmer said it was "fantastic" to welcome Poulter to the party
"The split in the BNP is imminent. It is reflected in a recent book written by BNP leader Moudud Ahmed," he said at a discussion in Dhaka on Thursday.
Mahmud made the claim soon after the formation of the National Democratic Front (NDF), a breakaway group of the BNP-led 20-Party Alliance.
The NDF, led by NPP chief Sheikh Shawkat Hossain, is a 10-member formation. Five of these parties are in the BNP-led coalition.