For more than five decades, countless non-government organisations (NGOs) have been seeking to bring positive change to Africa, investing huge amounts of time and energy to help those in desperate need. In the fight to eradicate poverty and conflict and improve the rights and conditions of women and children, many are doing superb and valuable work - but others are not.

A number of NGOs - most of which are driven by western funding and ideas - are household names, while others are micro-projects that are off the radar of most media but are nevertheless helping to improve the day-to-day lives of many Africans. Yet there are also many wannabe rescuers who are actively doing harm in Africa: bad ideas are duplicated across the continent, objectives and deadlines missed or efforts badly targeted, and promises broken, while mediocrity and incompetence are rarely challenged, leaving the poor ending up where they started. In extreme cases their work is not only inadequate but actually destructive in social, economic and environmental terms, crushing the hopes and dreams of millions.

Given what is too often a lack of accountability and credibility along with the huge funds that pass through NGOS, there are growing calls for closer regulation. We also need to end the often corrupt relationship - characterised by favouritism and bribery - between certain NGOs and some African governments. This situation cannot continue.

A good example of a bad but well-intentioned idea arose a few months ago, when a young US entrepreneur called Jason Sadler launched a campaign called "1 million t-shirts". His aim was apparently simple: to collect 1m new or used t-shirts, each donor enclosing $1 towards the cost of shipping them to Africa, where they would then be distributed to the grateful, t-shirtless masses. At the time, the project's website gushed: "We're going to change the world".

Little did he know – with his self-confessed ignorance of Africa and African development – that he would unleash a barrage of outraged criticism from the aid community and development watchers. I was one of the angry people who talked to Sadler at the time, but I'm glad to say that he has listened and learned. I am now helping him in an advisory capacity to transform his initial idea into something constructive.

The 1 million t-shirts saga fanned what is now a heated debate about the role of wannabe NGOs. In its initial form, the project epitomised what is wrong with so many attempts to "do good" in Africa; an ill-conceived idea imposed from outside by people with no understanding of the continent's needs: economically inefficient, damaging to local economies and an end-product that nobody needs or wants.

The fact that bad ideas can get off the ground at all is proof of the persistent ignorance and prejudice surrounding Africa among otherwise well-meaning people. It should come as no surprise, therefore, that many NGOs fail to see the damage they are doing. With "1 million t-shirts', I and other bloggers and activists were able to open Sadler's eyes and persuade him to change tack. But many problems remain. Why is it so easy to apply for charity status and then to start projects that are positively detrimental to Africa's interests, with no trail of accountability and sometimes no clearly-defined mission statement? Why are NGOs that are actually making things worse receiving funding and operating in Africa?

Although many NGOs are doing constructive, valuable work in Africa, the multitude of unmonitored organisations active on the continent – and the harm some do – is fuelling calls for tighter regulation. Governments are already taking steps in this direction – under British charities law, organisations with income exceeding £1m must annually provide details of how much is spent on fundraising and of the public benefit of their work. But we need to go further.

All non-profit organisations would benefit from having a dedicated authority responsible for regulating the sector. A single, comprehensive, publicly available database on NGOs providing a detailed description of their work and their fundraising activities is also needed. Such an independent authority could also promote good governance by disseminating a code of good practice and accrediting NGOs that voluntarily adopt these principles.

The ultimate beneficiary of tighter regulation, however, would be Africa itself. We need to recognise that some NGOs have failed and are still failing the continent. Too often, there is a huge gulf between the reality of the harm they are doing and their perception of themselves as saviours. It is time that Africans are able to say "thanks but no thanks" to bad ideas.

So what makes a good NGO? The formula is simple. It will have a sound, carefully thought-out core idea, with an organisational structure that enables good execution on the ground. It will not compete against other NGOs but rather share its expertise and experiences, both positive and negative, and thus both avoid a duplication of bad ideas and make good ones even better. It will not forget the positive values that were presumably a driving, motivational force at the beginning. Above all, it will consult local communities, gain their support and ensure they have a direct role in the project – without this any idea is doomed to failure.

Some NGOs put these principles into practice, but too many do not. Ultimately, we need to reach a point where all our efforts are being directed at encouraging those bringing positive change, rather than using valuable energy obstructing those who give the whole sector a bad name.