A senior Conservative MP has accused the RMT union of "co-ordinated contempt" for the travelling public. House of Commons leader David Lidington, who was stepping in for Theresa May, launched the attack at Prime Minister's Questions (PMQs) on Wednesday (7 December).
The comment came on the second day of the RMT's 72-hour-long strike action on Southern rail. The drivers have walked out in a long-running dispute over the role of conductors on the network, while other operators represented by the RMT's sister union Aslef are taking part in an overtime ban.
Mick Cash, the general secretary of the RMT, later hit back at Lidington.
"With the Tories now in open war over rail policy, with senior conservative MP's calling for [Transport Secretary] Chris Grayling's resignation, this is no time for mudslinging and lies from their front bench," the trade union chief said.
"It's a time for cool heads, serious talks and an end to the 'yah-boo' approach to the Southern dispute from both the government and the company."
Grayling has offered to meet RMT officials for talks, but only if the union suspends its industrial action. Govia Thameslink Railway (GTR), Southern's parent company, has warned its customers of "severe and significant" disruption throughout the strike.
The company has applied to the High Court in bid to stop Aslef's overtime ban.
"Regrettably, because of this wholly unnecessary and unjustified industrial action, there will be severe and significant disruption on our network from now on and customers are advised that stations will be incredibly busy, especially on the days Aslef is taking strike action," said Southern director Alex Foulds.
"If passengers can make alternative travel arrangements they should, and if they don't have to travel they shouldn't. If the drivers' strikes go ahead, there will be no services on Southern and customers should not attempt to travel.
"This industrial action is a clearly co-ordinated and cynical manoeuvre by the unions to bring yet further travel misery to passengers, as well as having a detrimental impact on the regional economy when it least needs it."
The travel turmoil caused by the dispute has even prompted an intervention from a group of Church of England bishops in Sussex.
"In the context of this rail dispute, we assert the moral obligation of all parties in this dispute to consider first and foremost their duty to provide reliable public transport," the Bishop of Chichester said.
Brighton Hove Albion FC have also offered to host peace talks between the unions and management at its stadium. The RMT has accepted the offer, but industrial disputes are usually settled at mitigation service Acas.