  We consider Benjamin-Bona-Mahony (BBM) equation of the form $$
u_t+u_x+uu_x-u_{xxt}=0, \quad (x, t)\in \mathcal{M}\times \mathbb R $$ where
$\mathcal{M}= \mathbb T$ or $\mathbb R.$ We establish norm inflation (NI) with
infinite loss of regularity at general initial data in Fourier amalgam and
Wiener amalgam spaces with negative regularity. This strengthen several known
NI results at zero initial data in $H^s(\mathbb T)$ established by Bona-Dai
(2017) and ill-posedness result established by Bona-Tzvetkov (2008) and Panthee
(2011) in $H^s(\mathbb R).$ Our result is sharp with respect to local
well-posedness result of Banquet-Villamizar-Roa (2021) in modulation spaces
$M^{2,1}_s(\mathbb R)$ for $s\geq 0$.
