Why should they need to know your financial information?
They might need a bank account to pay you .. that's about it.
Oh .. and the ability to afford transport to work and a clean shirt and trousers.
They need to know if you have been made bankrupt within the last three years, and will do credit checks on all your previous addresses in the last three years and do a criminal record check.
I only work in retail but they did a scottish disclosure and a CRC plus a credit history check on me, most companies do that now as it means they can be insured for you working there if you are handling cash.
My sister went for a job at Nationwide and they went through all her financial history for the last five years. Because she has defaulted on a credit card with a high balance she failed their test and wasn't hired just because of that.