Brown's response (below) was to say that cannabis is very dangerous and unacceptable, and then he went on to explain why alcohol, even though it causes harm, is legal.
At no point does he mention even mention tobacco, even though the Dowing Street web team responsible for the YoUTube channel titled the original question video "Ask The PM - Why Is Tobacco Legal?"
Isn't it good to know that when an oridinary person asks Gordon brown a question he ignores it and answers a completely different one instead? Had he been honest he would have said "well look, if it wasn't for tobacco tax revenue we'd be really really screwed rather than just screwed".
Also worth noting that on the Dowing Street Channel they say that Brown's responses have been posted by a user called "askthepm" which links to an independent YouTube site.
The profile for the site Dowing Street are bizarrely linking Gordo Brown to is one who's profile says
DowningSt doesn't allow party political questions - but we do! Everyone can post videos or comments here without censorship. So go ahead ... Ask the PM anything here. If you're looking for the official 'approved' site then search for downingst.
Seriously, can these people get anything right? First they get Brown to respond to a question by not even bothering to address it (that may just be him rather than them in fairness). Then they link Brown's responses to a site set-up to take the piss out of the "Ask the PM" features.