Who have to pay the council tax: a tenant(me) or a landlord, if they haven't got a written tenancy agreement? Before the tenant moved in the landlord told me that I shouldn’t pay the council tax. But after 3 years passed the landlord says that I should have paid the council tax for the whole period of tenancy. It is a one bedroom flat in London.

What should the tenant do to avoid this and obtain justice?

Think, in most ca=ses its the tenant who is responsible for c-tax. it should be clear from your tenancy agreement who's paying what.

Hello there goodfella,
I have had grief over council tax as well with my landlord so i can offer a little advice.
If your a full time student living in that one bedroom flat then your exempt from all charges as students dont pay council tax at all. However i dont know your employment status from your post so you'll have to let me know whether your working or not. If your working part time and on a low income you'll get partial council tax benefit towards your council tax costs. If your unemployed you'll get maximum council tax benefit towards your council tax like students and wont pay anything at all. Now the important part... If your working full time on a decent income you are liable for all council tax charges. BUT! Heres the loophole which may offer you a way out of this. Check your tenancy agreement, if your landlord has anything about him he will have written in that you the tenant is liable for all council tax charges. If he hasnt done this, you can technically argue that you never agreed on who was responsible for the council tax when the tenancy was determined, as a lot of landlords include council tax and utilities in the rent. As theres no legal documentation stating your liable for the charges its your word against his. However if he has written it in the tenancy and you ve been working for that three year period your pretty much done for.
Let me know a bit more about your employment status and i'll try and find the best way forward for you.

Hang on ive misread your post. You say you havent got a written tenancy agreement?
Well you have nothing to worry about then. Also if he told you at the start of the tenancy that you werent liable then your not liable. A verbal agreement between landlord and tenant is as valid as a written tenancy agreement.
If he takes legal action tell the court a verbal agreement was made between you and him when you picked the keys up.
There l only be one winner!