Stayed with out tenancy agreement - implications?

[Human]

I came here 2010 June 26. Since then, I have been staying in a property. Now the problem is that I don’t have a tenancy agreement. I am paying the owner rent on weekly basis.
I came to know recently that this may affect me in the longer run. What are the implications of this in my future PR/citizenship application (after 4 years)? Is there a way I can get out? Did I break the rules? Or is this my landlord’s fault? Can I demand a tenancy agreement from him now? Am I entitled to one as per UK rules?
I have bank statements to prove my residency here. Also I checked with the council, the owner has paid them council tax for this period (last 1 year) correctly. Are there other guys who are staying in friend's places etc without having them mentioned in the agreement? Please advice.

[batleykhan]

Your landlord is by law obliged to give you a tenancy agreement if you are renting a property of him.

It is in both yours and your landlords interest to draw up a tenancy agreement as it will give you both rights and protection in case of a dispute.

You can download a standard short hold assured tenacity agreement free from the internet.

Simply giving you a rent book will not suffice and will not protect you from eviction from the property etc.

It will not affect any application for PR/citizenship though

[mulderpf]

A rent book is all that is legally required, a written tenancy agreement is not, but could protect you in case of legal issue.

Also, it is not you that's broken the law here, it's your landlord, so it will not affect your applications in the long run.