Labour frontbenchers are standing in solidarity with railway unions by appearing at picket lines outside train stations, despite warnings by Sir Keir Starmer they face the sack for doing so.

Several members of Starmer’s shadow Cabinet – such as Kate Osborne, the Shadow Northern Ireland Parliamentary Private Secretary (PPS), and Paula Barker, the Shadow Defence PPS – have ignored orders against joining any protests coordinated by the RMT Union. Labour whip Navendu Mishra also defied Starmer’s ban.

A leaked memo has revealed that the Labour leader explicitly forbade this: “We do not want to see these strikes go ahead with the resulting disruption to the public.

“However, we also must show leadership and to that end, please be reminded that frontbenchers… should not be on picket lines. Please speak to all the members of your team to remind them of this and confirm with me that you have done so.”

On Monday, Unite’s General Secretary, Sharon Graham, tweeted: “The Labour Party was founded by the trade unions and we expect Labour MPs to defend workers, by words and by actions. To instruct Labour MPs not to be on picket lines with workers speaks volumes.”

Anas Sarwar, the Scottish Labour leader, has also joined the walkouts in a dispute over pay and conditions. Other Labour MPs have expressed their support for the unions, including – but not limited to – Ian Lavery, Beth Winter, Zarah Sultana, John McDonnell, Dan Carden and John Tricket.

Deputy Prime Minister Dominic Raab said Labour had “actively encouraged the inconvenience commuters are suffering”. Party frontbenchers turning out in force on picket lines makes it a difficult allegation to refute.