I am applying for Canada Pension and Old Age Security and wonder if it will be affected if I am eligable for a UK State Pension. I am a resident Landed Immigrant in Canada

It will not affect CPP. That is based soley on your contribiutions.

The only problem that I am aware of (and this was only pointed out to me recently) is that according to the Social Security Treaty you are not eligible for OAS for any year you were insured by NI in the UK.

So I think it will work like this (though I have not researched it yet and would like to be corrected):

You worked and paid your stamp in the UK for 20 years then moved to Canada where you have lived for 25 years before retirement. You will get 20/30ths of the UK State Pension and 25/40ths of OAS.

You worked and paid your stamp in the UK for 20 years then moved to Canada where you have lived for 25 years before retirement. After moving to Canada you paid 10 years of voluntary NI contributions. You will get a full UK State Pension and 15/40ths of OAS.