UK-based railway safety and economic regulator Office of Rail and Road (ORR) has reported that the rate of rail passenger complaints in the country increased by 7.5% in 2016-2017.
Occasional delays and unreliability of the services by train operating companies in London and the South East have been cited as the primarily reasons behind this rise.
The data published by ORR showed that there were 29.4 complaints per 100,000 journeys in the period for franchised operators that amount to 540,000 rail passenger complaints in 2016-2017.
Roughly 69% of all complaints were made via email or webforms.
The report also revealed that nearly 88% of the complaints were closed within 20 working days, which represents a 3% decline from the previous year.
The punctuality of train services during 2016-2017 was the lowest since 2005-2006, as reported by the Public Performance Measure (PPM) that represented about 27% of all complaints.
Passenger satisfaction with the overall journey also witnessed a significant decline over the past year, as 81% of passengers were satisfied in autumn 2016 compared to 83% in the same period of the previous year.
The data also stated that 13 train operators had fewer complaints overall, while eight operators had a higher number of complaints compared to the year prior.
Virgin Trains West Coast and Virgin Trains East Coast were seen to be the two operators with the highest amount of complaints, followed by Caledonian Sleeper, Greater Anglia and CrossCountry.
The results also show that Virgin Trains West Coast and Virgin Trains East Coast had the highest rates of 154 and 109 complaints per 100,000 passenger journeys respectively, however the companies' rate of complaints were shown to have decreased by 15% and 32% respectively from the previous period.
Online ticket sales was the category with the second highest number of complaints after punctuality and reliability, with 7.3% of all complaints making reference to web-based ticket purchases.
The rail industry regards a complaint as being an expression of dissatisfaction by a customer about service, operating company or industrial policy.
The data compiled by ORR is sourced directly fro train operating companies themselves.