Last Sunday, the Vicar of Holy Trinity, Brompton (HTB), Nicky Gumbel, and his wife, Pippa, gave a talk entitled: "Mary: mother of women's liberation".

Both men and women were called to ordination, Nicky stressed. HTB had a "long way to go" to achieve a balance of men and women clergy and speakers. Leadership gifts, bestowed upon both sexes, must be "not frustrated but fulfilled".

While some might regard these words as a mere stating of somewhat dispiriting reality, I hope that they will prove to be significant. Despite being one of the most influential churches in the country, HTB tends not to join the public arguments of the Church of England, described by Justin Welby as a family shouting at one another in the garden. It didn't proffer a prominent voice during the debate on women bishops, for example.

A consequence of this, is that the leadership's beliefs on several issues are the subject of speculation. What I know is often gleaned from "off the record" conversations and anecdotes.

So, to hear the Vicar preach on women's liberation and admit that there is a lot of room for improvement in his own church is encouraging. This is particularly true given the expansion of HTB's footprint in the Church of England. In recent years it has produced more than 30 church plants and grafts, and it is clear that its ethos has become increasingly influential in the hierarchy. Only one of these related churches (not listed on the HTB website) is led by a woman. HTB's stance on gender has real implications for the wider Church.

Take a look at HTB's talks and it's striking how few are by women, and still fewer by its women clergy. In Sunday's sermon, Nicky's wife, Pippa, talked about reluctantly agreeing to do "a little bit" in it, explaining: "As a woman I want sometimes to be up here to give permission for everybody else to know you can do this far better than I can." While this is well-intended, it does reinforce an implicit message that a woman's best chance of preaching at HTB is marrying one of the male clergy. There are four women curates on the staff but when I looked through the talks put online over the past year, I could only find one by an ordained woman. It was good to hear Nicky describe Mary the mother, on Sunday. But I hope that we hear more sermons on the women described brilliantly here as the "grandmothers of Christmas", who do not fit the mould most likely to be visible and celebrated at HTB. I'm told that one of the most popular recent HTB talks this year was by Philippa Savile, a widow who preached on hope.

None of this is to say that progress isn't being made. It's encouraging to see that at St Mellitus, the training college that has some of its origins in HTB, just under half of the more than 200 ordinands (trainee clergy) are women. The Assistant Dean, Dr Jane Williams, argues that the model of training – context-based – works well for women, as well as men. "It means that they are exercising their gifts in ministry throughout their training, and also enabling their churches to see women training for leadership and priestly roles, thereby raising the profile of women in local churches," she argues. There was a force to Nicky's assertion, on Sunday, that "God is calling men and women." Within the HTB network of churches, including the 'plants of plants', there are a handful woman curates.

I am also told that there are still complaints whenever a woman speaks at HTB. Nicky's talk on Sunday helpfully provided a biblical basis for gender equality, in anticipation, perhaps, of more. He emphasised the revolutionary nature of Jesus's interactions with women: how he "repeatedly liberated and affirmed women, treating men and women as equals" and how, even in the Early Church, women began to experience "the liberation of the Kingdom of God". Galatians 3:28 was a "three-stage time bomb", he argued, with the third stage ("nor is there male and female") finally taking effect during our century. Helpfully, a database of women speakers is already being compiled, with this very verse as its calling card.

Nicky also acknowledged "shocking and widespread violations of human rights" and an ongoing "struggle for equality". He quoted his tutor at Oxford, Rev Dr David Wenham, who once wrote: "Just as changes in society made it possible and indeed imperative for slavery to be abolished, so discrimination against women in ministry has now had its day and should be ended."

The whole sermon had the feel of a manifesto: a clear and robust statement of belief and intent. It also contained a confession. There was a "long way to go", at HTB: "Balance of speakers, male and female clergy is not right yet. But we are working on it and we will get there."

Part of that work must surely involve asking challenging questions about how this imbalance arose in the first place? What attitudes lay behind it? What conscious or unconscious biases exist? What would it look like to confront these attitudes and dismantle the imbalance that has arisen? Is the desire to do so shared by all of the leadership? I hope women are given the opportunity to share their own experiences of the effects of the existing culture, and suggest possible solutions.

Aware of the potential for irony in his delivery of a sermon on women's liberation, Nicky argued that it was "not just a women's issue".

"It a men's issue as well, and we men have to face up to our responsibility in this. Mary began a revolution that would lead us to recognise God's gifts and calling. We need to treat people according to their God-given gifts and abilities, not their gender. Leadership gifts need to be not frustrated but fulfilled."

Leadership has become an important strand of HTB's work. In addition to its annual Leadership Conference it runs a Leadership College, seeking to train "young leaders who are called to develop their gifts and transform society". It's encouraging to see women featured in its testimonies, but notable that the vast majority of speakers advertised for its annual conference are men. Again, there is some way to go.

There is so much that is wonderful about HTB. But I hope that this talk accelerates long overdue action so that it truly reflects the diverse body of Christ. Without the gifts of women, and other unrepresented groups, the entire church is impoverished. Mary, as Nicky pointed out on Sunday, was the only witness to all three moments of our redemption: Incarnation, Passion and Resurrection. What encounters with the Good News could today's women give witness to? I hope we hear more in 2017.

Madeleine Davies is deputy news editor at Church Times, writing here in a personal capacity.