Compensation for sub-postmasters is not being decided by a “kangaroo court”, the body overseeing the payouts has said, pushing back against allegations made by Sir Alan Bates.

Sir Alan, who led the campaign for justice, said he had been made a “take it or leave it” offer that was less than half the amount he was claiming.

The “goal posts” had moved and claims had been “knocked back”, he said, in ways he saw as unfair to sub-postmasters, many of whom have been waiting years for redress.

However, the Horizon Compensation Advisory Board has rejected his criticism, saying it was following a process agreed by Sir Alan, designed to resolve the outstanding cases.

Writing in the Sunday Times, Sir Alan had suggested the process was not following established standards, describing it as a “quasi-kangaroo court”.

The board, made up of parliamentarians and academics, issued a statement on Tuesday saying: “We do not agree [with the criticisms].”

It said Sir Alan had been “closely involved” in setting up the process for deciding compensation, which included a final assessment from a “highly respected” judge.

“That was what happened in Sir Alan’s case,” the board said.

“It is only a ‘take it or leave it’ decision in the sense that at some stage the matter has to come to an end and someone has to decide, in order to bring fair closure to so many who have been harmed.”

Between 1999 and 2015, more than 900 sub-postmasters were wrongly prosecuted after the faulty Horizon IT system indicated shortfalls in Post Office branch accounts.

Sir Alan led a group of 555 sub-postmasters who took part in the landmark group legal action against the Post Office.

Their fight for justice was brought to wider public attention last year by an ITV drama about the scandal, Mr Bates vs The Post Office.

The government went on to set up a specific compensation fund to ensure these sub-postmasters received extra money to reflect the gravity of their situations, but progress has been described as slow and many are still waiting for a payout.

Under the Group Litigation Order (GLO) scheme, claimants can either receive £75,000 or seek their own settlement.

Sir Alan said the latest offer made to him amounted to 49.2% of his original claim.

He said promises that compensation schemes would be “non-legalistic” had turned out to be “worthless”.