Merton's main housing association Circle Housing Merton Priory (CHMP) has admitted contractors have been overcharging for repairs at its properties as part of a £220m contract.

Evidence of "mostly" overcharging, but also some undercharging by contractors Keepmoat Property Services was found after the 9,000-home housing association hired independent auditors to investigate whistleblowers' allegations published on this website.

Sept 4: Firm investigates whistleblower's over-charging claims

The full results of the audit - which involved a random sample of 25 homes in October last year - have yet to be made public.

But Circle Housing's senior executive Deborah Upton said today that despite the repeated overcharging there was no evidence of fraud.

She told the Wimbledon Guardian that the overcharging was due to contractors logging work under the wrong code due to an "argument" over what those different codes, known in the industry as schedule of rates, really mean.

She said: "It's not unusual that those types of things happen at the beginning of a contract.

"The contracts people use are industry-standard contracts but people interpret them in different ways because they don't go down to the last nut and screw and piece of ply board used and that's why there's genuinely a bit of wriggle-room."

She would not say if the scale of the overcharging found so far was in the region of hundreds of pounds or thousands of pounds.

The housing association has now hired property consultancy Savills to conduct a wider investigation into completed repairs to assess the borough-wide scale of overcharging for different jobs.

It will also suggest ways of improving the system to ensure more accurate charging.

About 18,000 repairs are completed every year by Keepmoat as part of a £220m, five year contract which began in January 2013 for responsive repairs across 17,000 homes in Merton and Kent.

Savills will not check all the repairs carried out but Ms Upton said the company will examine a sample of different types of repairs and then apportion the percentage of overcharging across all historic repairs and ask Keepmoat to repay the money.

She said Keepmoat has already agreed to repay the money for overcharged work within the 25-home sample.

The full results of the original audit will be revealed at the same time as Savills publishes its findings of its wider investigation. Ms Upton said this was likely to be in May.

The housing association has faced strong criticism from MPs, councillors and residents for failing to publish the results of the audit sooner.

Circle Housing senior executive Deborah Upton 

Ms Upton first said the results, which were known to her in November, would be made public after a board meeting in March.

She said today the board, which includes Councillors Laxmi Attawar and Marsie Skeete, as well as senior finance, engineering and corporate consultants, has been shown an interim report but will not be shown the full report until Savills has completed its investigation.

CHMP has yet to say whether leaseholders will be repaid for any work for which they have been overcharged.

Circle Housing Merton Priory HQ in Morden 

CHMP already surveys all works completed over £500.

Following the audit revelations, 20 per cent more jobs under £500 are being surveyed.

It has increased the number of jobs under £500 which are surveyed by about 20 per cent.

Keepmoat has yet to comment on today's announcement by CHMP.

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