Train operator Abellio Greater Anglia (AGA) has recorded the biggest rise in the number of passenger complaints in the UK over the last year, according to a new report.

The Office of Rail and Road (ORR), the UK’s rail regulator, found that the number of complaints per 100,000 passenger journeys at AGA increased from 35 to 62.3 from the second quarter of 2014/15 to the same period in 2015/16.

It was a rise of 77.9%, which was the highest out of 16 rail operators included in the report. Ten of them saw a fall in complaints during the same time.

Areas identified for improvement included the quality of heating and air conditioning on trains, buying tickets online and at ticket machines, wrong tickets being sold at ticking machines and refund policies for advanced tickets.

An AGA spokesman said: “The rise reflects a change in the shape and size of the rail network we operate.

“The franchise area altered in May 2015, when a number of services were devolved to the Crossrail and London Overground franchises.

“These devolved services generated fewer complaints in proportion to the rest of the network.

“Comparing the current franchise area on a ‘like-for-like’ basis, year on year, we saw a slight increase in complaints which reflected a slight increase in service disruption over the period covered.

“We have also continued to make it easier for customers to contact us and to claim compensation, and we now offer redress in the form of a cheque as well as rail vouchers.

“These factors also play a part in encouraging an increase in complaints.

“During the current short franchise we are investing more than £40m in customer-facing improvements, including customer service upgrades, better cleanliness, station enhancements and train refurbishment programmes.”

The ORR report also found that AGA has increased the number of complaints to which it responds, rising to 98.4% in 2014/15.