OP - we had this this summer when we moved and I was on maternity leave. My salary is about 75% of our household income. At the time of the application (again, to our existing lender) I was on SMP, but returning FT in c3 months.
The woman on the phone was very "computer says no" based on what I earnt that week. I asked her to speak to someone else, and she came back also straightaway saying that it would be fine with a letter from my employer about my return and my salary, plus they could look as much as 3 months ahead for salary projections, so could make the lend.
I do understand that many women do not eventualy return to work, even when they intend to (as per DisplayBefore). I also understand that there need to be sensible lending criteria and calculated risks. However, some of the expectations put on women do rankle. Not least the idea that I might not return to work - even though we've just taken out a great big mortgage! And I make the money in the house.
So, in actual fact, perhaps a 3 month look-ahead period is not a bad compromise. The baby is born, so you know whether there might be immediate problems preventing you from going back, and you have a sense of what family life is now like. But blanket refusals on women purely because they are on maternity leave does seem to border on discrimination.
ps - on your working environment. That is toxic. I too am a city solicitor, have been at a couple of different firms in various departments and cities, and have never had what you've experienced.