Labour MPs who signed a Stop The War Coalition letter slamming NATO and accusing the UK of "sabre rattling" over Ukraine were threatened with suspension, the Mirror understands.
Some 11 Labour MPs signed the open letter by the left-wing campaign group, which questioned NATO's legitimacy and accused the defensive alliance of "eastward expansion".
It also claimed the UK Government of having "no proposals for a diplomatic solution to the crisis" and says "Britain needs to change its policy, and start working for peace, not confrontation".
