Post Office lawyers will come under scrutiny again next week as victims of the Horizon scandal detail their battles for compensation.

Responding to a freedom of information request by the Gazette, the Post Office revealed this week that it spent £23.6m on external legal advice relating to compensation schemes in the year to 31 August.

Wrongly convicted sub-postmasters continue to believe that their claims are being overscrutinised, with individuals asked to produce evidence going back more than 20 years.

The independent advisory panel set up to assess cases has members from a mixture of legal, forensic accounting and retail backgrounds. Claimant lawyers have told the Gazette that the panel lacks resources and has met less frequently this year than in prior years. Some cases awaiting redetermination go back to March, and sub-postmasters are waiting months for offers.

These issues will be aired at the Post Office Inquiry next week, when general counsel Ben Foat is due to give evidence.

Herbert Smith Freehills and Peters & Peters advise the Post Office on two compensation schemes, while the Department for Business, Energy & Industrial Strategy instructs Addleshaw Goddard and Dentons on two more. The fixed-sum award options are £75,000 in the HSS and GLO Schemes, and £600,000 in the overturned convictions scheme. These schemes are voluntary and postmasters who believe their claims are worth more can go to a full assessment.

The Post Office said the costs of running the schemes reflect the huge scale of the scandal. A spokesperson said: ‘Working alongside government, we are focused on paying redress as swiftly as possible and around £363m has now been paid to more than 2,900 people affected. We’ve continued to listen to feedback and make improvements, and the government’s introduction of fixed-sum options without the need for postmasters to submit formal claims is also helping to accelerate settlements.’

Solicitor Neil Hudgell, whose firm represents dozens of sub-postmasters, urged the government to work on ways to simplify the schemes. He added: ‘It remains the case that processes are overengineered, convoluted and inconsistent. The overwhelming message remains – pay what is reasonably claimed. And do it quickly.’