Only affiliated ones contribute to Labour which RMT or Criminal barristers are not.
Explore the different trade unions affiliated to the Labour Party.
labour.org.uk
Incidentally RMT were the biggest Brexit supporting Union,
Labour have problem when its Unite or Unison or other front line health and social care affiliated Union are on the picket, but then so do the Conservatives, pots and pans at 8pm on a Thursday wont cut it this time.
For some unknown reason, lots of people seem to want Starmer to walk willingly into Johnson's obvious traps even though he doesn't need to...I dont see any point in Starmer behaving in a similar manner as the previous Labour leader.
I don't think this is a valid stick to beat Starmer with this at this conjecture. However, gloves will need to come off, but closer to election time and myself would hope the process begins Party Conference time. Right now let the Tories keep on burying themselves, give them no ammunition to shoot back with.