Payment option 'none' disappeared when creating account

When creating a new iTunes account, the option to select no payment option ('none') has disappeared. The only options available are Visa, Mastercard and Amex.
Have tried this on both an iPad an an iPhone and the option is not available.

I've created a number of accounts over the past 2/3 weeks and the option was available then.
Anyone else having this problem or know what we can do about this?