Dave,
It is what you said and it is there for all to see

Yes, and hear it is again.

"I suspect that it is because other parties do not have such a problem, as Labour did not until recent times."

No wriggling from me Dave.
I do indeed suspect that, and I stand by it.

The reason I think other parties do not have such a problem is that

A.Their women MPs do not write en-masse to complain like Labour's do, and

B. Because there is a "Labour Too" movement but no equivalent for any other party.