Southern Railway passengers face fresh disruption from the end of the month because of a ban on overtime by drivers after the firm revealed it had offered employees a four-year pay deal worth 23.8%.

Govia Thameslink Railway (GTR) said the offer would take a driver's base salary from £49,001 to £60,683 for the existing 35-hour, four-day week.

Details of the offer were released after GTR said it had been notified by the drivers' union Aslef that a ban on overtime will start on June 29.

Services were badly disrupted the last time Aslef launched an overtime ban.

Aslef and the Rail, Maritime and Transport union are embroiled in long-running disputes with Southern over staffing and driver-only trains which have sparked a series of strikes and other forms of industrial action for more than a year.

Proposed agreements between Southern and Aslef's leaders have twice been rejected by the union's members.

A spokesman for GTR said: "The Aslef leadership has twice accepted the extension of driver-controlled operation and asked us this time to package it up with a pay deal.

"We've made a very generous offer that in four years would take a driver's base salary to £60,683 for the existing 35-hour, four-day week, so we find this threat of an overtime ban surprising and extremely disappointing.

"Our passengers have enjoyed six months of sustained improvements in service levels since we extended driver-controlled operation.

"Passengers will rightly ask why the union leadership has now announced more disruption through industrial action.

"We are modernising and future-proofing the most congested and fastest-growing part of the UK's network for passengers, whose numbers, to and from London, have doubled in recent years.

"This change includes extensive infrastructure rebuilding and upgrades, new trains and technologies and a change in our working practices to allow more trains to travel through the network.

"We are still in transition but we are starting to see performance improvements."

In an internal company email, Angie Doll, Southern's passenger services director, said she was assuming Aslef will be rejecting the pay offer even though no formal response had been received.

She said many drivers will be unhappy if the pay offer is rejected and further industrial action taken.

Aslef general secretary Mick Whelan said: "Aslef suspended the imposition of an overtime ban on Southern Railways, due to start on June 4, for two weeks to allow time for negotiations to find a resolution of all the outstanding issues with the company to be discussed.

"For the record, we have only ever talked to the company about driver-only operation (DOO), not about driver-controlled operation. That is just one of many inaccuracies in the press release the company has issued.

"We have been talking to the company over the last fortnight, in parallel, but separate, talks about drivers' terms and conditions; industrial relations; and pay.

'The company's failure to engage over DOO is the reason our members will no longer work overtime, which, of course, is entirely voluntary, from June 29.

"By giving the company another fortnight, we had hoped to avoid industrial action because industrial action is always the last resort. We would much rather talk, and negotiate, around a table, than take industrial action.

"As for pay, that is now eight months behind schedule, on a deal that should have been done back in 2016, but which the company has refused, until now, to negotiate with us.

"I can categorically state that the company spokesman is lying when he says Aslef asked GTR to package up an extension of DCO with pay. We did not.

"That is a blatant lie and a deliberate and malicious attempt to mislead the passengers this company has been letting down, every day, since it got its franchise.

"GTR should stop letting passengers and staff down and stop telling falsehoods. Because this is no way to run a railway."

Mr Whelan again called on Transport Secretary Chris Grayling to intervene and help resolve the dispute.