The group behind strike-hit Southern Railway has pledged to fund 50 on-board supervisors as part of a £13.4 million deal with the Government to fund improvements for long-suffering passengers.

Govia Thameslink Railway (GTR), which is run as a joint venture between Go-Ahead and French firm Keolis, said it had reached a long-awaited settlement with the Department for Transport (DfT) over its poor performance amid 18 months of strike action.

It will pay £4 million to fund 50 on-board supervisors from next January for two years, while £7 million will be put into a fund for the DfT to allocate towards projects and improvements to benefit passengers.

The remaining £2.4 million will go towards target performance improvements and GTR must submit plans on how it will do this to the Government.

Southern has been involved in a bitter dispute with unions over proposals for driver-only operated trains, with conductors holding more than 30 strikes in the past year, while drivers have separately walked out due to the row.

But the railway has also been impacted by extensive improvement works, with GTR admitting it had "underestimated" the impact of this on the service.

Charles Horton, chief executive of GTR, said "We are pleased that this issue has been concluded, and accept and are sorry that our service levels haven't been good enough for passengers.

"We run the most congested network in the UK where passenger journeys have doubled in the last 12 years.

"This has meant we have been running services for more and more passengers while also allowing stations to be rebuilt, platforms extended, track and signalling replaced and new trains and technology introduced too."

Go-Ahead said the £13.4 million settlement, which will impact its rail arm profits, was "very close" to expectations.

But it said annual rail profits could still be hit by up to another £5 million due to ongoing talks with the DfT over contract changes, such as a timetable overhaul.

The group said the agreement "resolves financial uncertainty relating to past industrial action and allows GTR to focus on improving services for Southern customers".

But the funding package, including plans for an on-board supervisor, is unlikely to soothe trade union anger with members of the Rail, Maritime and Transport union last week staging their 33rd day of action in a row over plans to change staffing on trains.

GTR insisted its network overhaul had started seeing a performance improvement "consistently" over the past six months.

It added: "GTR now hopes that the trade unions will play their part in the modernisation programme too, so that passengers finally get the benefit of all the transformation work that has been and continues to be delivered."

GTR is run by Govia, which is 65% owned by Go-Ahead and 35% owned by Keolis.