It's not like the election was last week and they stood for Labour then quit as soon as they won out of some act of deception. Half of them have held their seat since 2010, the other half even longer than that. I think being a party's MP for 8 years (two of them have been for 26 years) then resigning shows they feel the party doesn't match up with their core beliefs any more.

Their constituents voted for them, not Labour. This is a failing of the voting system in this country, that can't be helped by any of these seven MPs BUT I agree that a by-election would be the right thing to do in order to confirm their constituents' trust in them. I don't even know what they stand for yet, but I don't see how resigning from 1 of only 2 parties in this country able to win an election is 'self-serving'.