‘DON’T go that way, there might be snakes,” says Mette. We keep to the trampled path that leads to the inflatable white tent. Inside a front room sits a nurse at a desk full of contraceptives and leaflets, through the back, a consulting room where women can get an IUD or implant fitted on the spot.

The set-up is part of a festival-like event which includes contemporary African dance, a DJ with a pulsating sound system, and groups of young people discussing family planning methods under the shade of nearby trees.

We are in Bagamoyo, 50 miles north of Dar es Salaam, Tanzania’s largest city. I’m here during the parliamentary recess on a five-day trip with Conservative Baronesses Jenkin and Hodgson, and Labour MPs Kim Johnson and Apsana Begum, supported by our organiser Mette Kjaerby. All of us from the All-Party Parliamentary Group On Population, Development And Sexual Health. The title is a mouthful – it’s basically a cross-party campaign to improve women’s reproductive rights across the world.

For us, that means finding out what the UK Government is doing through the Foreign, Commonwealth and Development Office (FCDO) and building pressure to make it do more, better. Today’s event has been made possible by funding from the FCDO. Future ones are now under threat as funding reduces.

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At a global level, the link between sexual health and rights and unintended population growth was established decades ago. The UN set up a dedicated agency – the United Nations Population Fund (UNFPA) – to co-ordinate efforts and it is under their auspices we are here.

Tanzania was run by Britain when I was born. In 1961, it became an independent republic and Julius Nyerere, the man who had led the independence movement, its first president. The country Nyerere established had 10 million people. Today it has 62m. The population has doubled in the last 20 years and is predicted to double again by 2050. It is the eighth fastest-growing country in the world, and a good place to start if we are going to manage global population at sustainable levels.

Worth noting, the land mass is five times that of Britain, and there are large areas of fertile land yet to be cultivated. Those hostile to birth control say that, unlike many countries, Tanzania can feed itself even with a growing population.

Even if that were true to some extent, there are still numerous benefits to reducing the birth rate – for not only the women and girls involved, but the country as a whole. Besides, the continuing influx into urban areas means services are already under pressure. With increased arrivals from the country, numbers will swell to crisis point.

Dar es Salaam is a massive urban sprawl. It has grown rapidly with inadequate planning or investment in the infrastructure required to cope with a huge population. The roads are good but already full of traffic and there is minimal public transport.

Despite a network of bus-only expressways under construction it is hard to see how it could double in size without serious collapse. That point is accepted by the government officials and ministers we met, all of whom are now behind the drive to give women choice and access to contraception.

The current fertility rate is 5.8 – far higher in the rural, poorer, areas outside the cities. Admittedly, that is down from a high of over eight some years ago. Everyone knows that figure isn’t sustainable. No-one will put a figure on what it should be, and targets are eschewed for fear that they might seem draconian and lose public confidence in the process. But everyone we spoke to was clear – it has to fall.

So, all efforts are now going into scaling up family planning. The key is expanding access to modern methods of contraception. Currently, about two in five women of reproductive age (15-49) are using some form of contraception. Probably around 10% will have fertility problems. That leaves almost half – eight million women – who are not currently planning their pregnancies.

Agencies say that almost half of that number have already had some interface with the health system – typically when giving birth – and have been offered contraception but are not using it. UNFPA calls this category “unmet need”.

Unmet needs will have to be met, and that requires a range of approaches. Making sure the distribution and supply of materials is up to scratch and women can get the right product at the right time is one. That’s the easy bit.

Much harder is trying to overcome the attitudes embedded in communities steeped in a strong culture which keeps myths alive. This is most intense in the more rural areas and amongst nomadic communities where the birth rate is considerably higher.

Many young women still believe that using contraception will make them infertile. We heard stories of women ostracised from their villages because they chose to use contraception – the social pressure not to is intense. Nonsense about contraception reducing sexual desire – for men and women alike – is also commonplace.

There is still a strong belief amongst these harder-to-reach communities that bigger families are better. They see more mouths to feed as more than offset by more youngsters to work the land.

Sometimes this is enforced by more than ideas. Agencies working with women who have suffered domestic violence report how they will be more of a target if they are known to be using contraception. There are stories of men cutting implants out of their wives’ arms, leaving them to be patched up by mobile clinics.

Until not so long ago these attitudes were tolerated by the government. The former president John Magufuli was well known as a sceptic when it came to family planning, seeming at times to promote procreation as a form of personal and national virility.

That’s changed. Serious work is now under way to reach those not already being offered birth control. We saw a range of creative and imaginative approaches to both increasing services and encouraging their take-up.

Mary is a retired nurse. She now works as a community outreach volunteer in a village health facility run by Marie Stopes Tanzania (MST). She talked to me about her job knocking on doors and speaking directly with women to encourage them to come to facilities like hers. Between the health ministry and the main NGOs, there are around 20,000 Marys and they are reaching hundreds of thousands of women every month.

There is a particular problem with teenage pregnancies – 22% of young women are pregnant before 18. Impressive work is going on at a granular level to reach them. Umati is an NGO which runs a number of youth centres offering recreational activities combined with sexual health education and direct provision of contraception. The clinic we visited sees 35 young people every day. On Saturdays, they take over the local health service clinic and run it for young people who are in school through the week. Sadly, that’s now under threat as a result of our Foreign Office stopping funding in December.

Suzana Mkanzabi runs Umati. “The key to success is the empowerment of young women” she tells me. “We know once they reach 18, they have more agency and confidence to make their own decisions, to have a choice.”

Government policy is now being directed towards that end. In 2015, the law changed to mandate seven years of primary and four years of secondary education for all.

So, although there is no legal school leaving age, since primary usually starts at seven, this should keep most in the system to around 18.

But it is taking time. Parents keep kids home saying they cannot afford the associated costs of uniforms and materials, and enforcement varies.

Campaigners also hope this year will see the age of marriage consent raised from 14 to 18 – a move which many say will push the average age of pregnancy upwards.

Things are moving in the right direction but there is a race to reach, educate and service the country’s 16m women of reproductive age before it is too late – to build a virtuous cycle instead of a vicious one. And in doing that, the many passionate Tanzanians we met need our help.

This is the sharp end of the debate on aid funding. This is where the cut from 0.7% of GDP to 0.5% kicks in. It’s time to reverse this Conservative mantra and for this rich country to once again be seen as a leader rather than a shirker when it comes to doing the right thing.