Prime Minister Malcolm Turnbull and his ministers have slammed One Nation leader Pauline Hanson's proposal of a so-called "Muslim ban" in the wake of the London terror attack, arguing her policy is dangerous and would worsen the impact of terrorism.

In a provocative video published hours after the London attack, in which four people died, Senator Hanson noted the hashtag #PrayForLondon, which was being used to express sympathy around the world.

"I have my own hashtag ... it's #Pray4MuslimBan," she said." That is how you solve the problem. Put a ban on it and then let's deal with the issues here."

Her office clarified she was advocating One Nation's existing policies on Islam - such as a ban on Muslim immigration and an inquiry into whether Islam is a religion or political ideology - not prohibition of the practise of Islam.