The British Association for Shooting and Conservation (BASC) said the current "robust" system of licensing was based on "sound evidence" and ensured that guns did not fall into "unsuitable hands".
It comes after West Midlands Police and Crime Commissioner urged the Home Office to allow forces to recoup the total cost of administering firearms licences after his own force reported a £170,000 loss for processing certificates last year.
The BASC have told Mr Foster to focus on his force's poor performance on licensing, after West Midlands Police were ranked one of the worst performing forces in the country for providing the service.
In 2020 West Midlands Police took an average of more than 15 weeks to renew a licence - the third worst record of any force in the country.
Lewis Thornley, central England director for BASC, said: "Simon Foster’s argument for increasing firearm licensing fees comes on the back of the West Midlands' licensing team being one of the worst-performing services in England and Wales.
"The 2015 Firearms Licensing Fees Working Group set about a system that is based on sound evidence and complied with Treasury guidelines. On that group and agreeing to the costs set for firearms licensing were police representatives including the current West Midlands firearms licensing manager.
"The British Association for Shooting and Conservation (BASC) believes the robust process of licensing ensures firearms do not fall into unsuitable hands – this is a public service and the public purse should rightly bear a share of the cost."
He said there were 10,000 firearms certificate holders in West Midlands who required firearms "legitimately" and were "crying out for an improved service".
He added: "When neighbouring forces continue to work efficiently and effectively under the current system, serious questions remain about the West Midlands’ service."
The BASC say they have offered Mr Foster the opportunity to meet to discuss firearms licensing.
Mr Foster says that under the current system the cost of carrying out safety checks is greater than a licence fee.
He said: "It cannot be right that police forces should have to effectively subsidise gun ownership.
"The Home Office should allow PCCs to charge what it actually costs forces to process the licenses."