As of today, the Child Support Agency will now charge £10 for applications made to them for personal information. They say that requests for information on the following will be free of charge:

- How someone's child maintenance has been calculated.
- Copies of any letters they have sent.
- An update on a CSA case.

However, for all other information, written requests must be made and must include:

- full name
- date of birth
- address and telephone number
- CSA case number, and
- National Insurance number.

They say that the fee "helps with the costs of dealing with your request" and "is in line with the Data Protection Act 1998."

More here CSA charges

It is true that government departments can charge up to a maximum of £10 for copies of a person's records under the Data Protection Act. They don't have to, and some don't charge at their own discretion, but they have the legal right to do so.
If you are funded through a legal aid contract you can claim a disbursement to pay the fee, if you're not it's a problem. In a previous job I've had to ask clients if they can pay the fee for copies of information because we didn't get the type of funding that would cover it. It's not unreasonable to ask someone in work to pay the £10, to my mind, but it's completely unaffordable for someone on benefits. I have persuaded GPs and local government departments to waive the fee for claimants, but have never had to ask the CSA. So I don't know how they'd respond to such a request.