RMT claims rail dispute deal 'approved by Chris Grayling'
The RMT is calling for talks with the transport secretary amid claims he has signed off a deal with another union in one of the UK's longest rail disputes.
Two unions have been in dispute with Govia Thameslink (GTR) over driver-only-operated trains.
The alleged deal is between Aslef and GTR but they both said they were still in talks.
A letter from the RMT union to Chris Grayling said he would have approved any deal and demanded full disclosure.
When approached for comment, the Department for Transport referred the BBC to GTR, the parent company of Southern rail, which has seen more than 30 days of RMT strikes over the past 16 months.
In a letter to Mr Grayling, RMT general secretary Mick Cash said: "I am hearing reports that a deal has been agreed with Aslef and GTR regarding the driver-only operation dispute.
"Any deal reached with Aslef will have had to be approved by yourself as you are directing this dispute and we understand you have agreed the deal."
He added: "It is imperative that Mr Grayling and his contractors, GTR, give full disclosure to the deal that has been put together and engage with us in further face-to-face talks aimed at reaching a safe and sustainable solution to this long-running dispute."
Aslef said there was no deal on the dispute or other issues.
A GTR spokesman said: "Discussions with Aslef are ongoing and we continue to work hard to reach a resolution."
RMT members plan to walk out on Friday and Monday on Southern and Arriva Rail North, which operates under the brand Northern.
Staff at Merseyrail will walk out on Friday, Sunday and Monday.
The RMT said it still had concerns over safety and job losses as a result of new working practices, but the rail operators said safety fears were unfounded and jobs would remain.