Mr Abbotts Wiki detailing date of birth and British father. Here
The file cover for the Australian citizenship application. Here
Assisted passage which shows his mother to be British now,no longer Australian. Here
The email from Oxford University showing he matriculated there in 1981 as a British citizen. Here
The FOI request showing renunciation papers do not exist. Here
Without the renunciation papers Mr Abbott is still a British citizen and a dual national. British law requires a form RN be filled in and the relevant fee paid. A copy of the UK paper work and information about renouncing citizenship is here.