Are pre-paid credit cards statements accepted as an evidence when applying for UK standard visa?

I agree with the detailed information in Burhan Khalid's answer. But just to make this perfectly clear: the action you are proposing will be considered fraudulent and will lead to certain refusal of the application.

The main problem is not the credit card (though this inadequate). The main problem is you sending your relative a large sum of money in an attempt to make them appear able to support themselves on the trip. This is known as funds parking, and it would be just as unacceptable if you deposited this money into a bank account.

Update: the "correct" way to do this is for the application to make clear that you, as a third party, will be providing the funds to support your father. This is allowed on the application. In this case, you will provide documenting evidence about your own financial situation.

See some information in the visitor guidance under "Maintenance and accommodation provided by a third party". There are also some related questions and answers on this site; here is one.

There is potential for a visa to be refused in this situation. If the person evaluating the application is not satisfied that your father has enough financial and other ties to his country to return, they may fear he intends to stay in the UK illegally (Unfortunately, it is a reality that people who are financially comfortable get visas much more easily than those who are not).