Hundreds of court cases a week are being disrupted because of the continued failure of a Ministry of Justice contractor to provide interpreters, official figures have revealed.

Statistics released last week show that the performance of the courtroom interpreter service provided by Capita fell in the first six months of this year compared with the same period last year, while complaints about it have soared.

In the first three months of the contract, which began on 30 January 2012, Capita fulfilled 76% of requests, rising to 92% in the second three months. The figure remained roughly the same for the rest of the year.

New provisional figures show the rate dropped to 86% in the first three months of 2013 and rose to 87% in the second three months.

Overall, in the 17-month period covered by the data – 30 January 2012 to 30 June 2013 – Capita received a total of 195,783 requests for interpreters from courts and tribunals.

On average it fulfilled 88.5% of them, leaving some 22,516 requests unfulfilled, meaning around 60 hearings each day faced disruption.

There were 9,800 complaints about the service from 30 January 2012 to 30 June 2013. Of those 39% (3,786) arose because Capita could not supply interpreters; 16% (1,530) because the booked interpreter did not attend; 15% (1,515) were due to the interpreter attending late; and 4% (410) related to the quality of interpreting.

In the second quarter of 2013 there were 1,957 complaints – 23% more than in the same period of 2012. Most  (64%) concerned interpreters not being available.

For the first time, the statistics show the number of ‘off-contract’ bookings, made where courts and tribunals contact interpreters directly rather than through Capita. In the second quarter of 2013 (the first period for which such data is available) a total of 2,929 off-contract bookings were made, accounting for 7% of bookings.

Justice minister Shailesh Vara (pictured) said that the contract with Capita had saved £15m in its first year. He said ‘dramatic improvements’ have been made over its life and that the ministry continues to ‘drive further improvement in performance’.

A spokesperson for Capita said: ‘We have seen a significant increase in fulfilment rates which are now tracking towards the target level of service required. A continuous programme of improvements is being implemented as we work together with stakeholders and this is showing a positive outcome.

‘The figures for Q3-2013 will demonstrate both a significant improvement to fulfilment rates and a reduction in complaints.’