Hi,
They have the records of the applications on there system even when they said they dont hold any information. Secondly does not matter if you apply with the new passport they will be able to track the old passport details and will easily find out that you did applied before. They asked this question because they know they can verify it so better to tell the truth rather than hide it and regret it later on. For whatever reason they refused your application if you are eligibile now then tell the truth.
Cheers
Saki