This is a pivotal moment for international transparency and open government. Just over a year after it was launched, the Open Government Partnership has 58 members, covering a third of the world's population. The United Kingdom is now lead chair of the partnership. We are at the helm of this transparency revolution.

During our chairmanship we are determined to turn the rhetoric of transparency into practical effect. We want to firmly establish the OGP as a credible and sustainable force for change. The theme of our chairmanship is transparency drives prosperity because openness has the potential not just to sharpen accountability but to drive economic and social growth as well.

Next week, I will host the first meeting in London of the partnership's ministerial Steering Committee. At the event we will launch a unique initiative - the Independent Reporting Mechanism. The mechanism will see civil society researchers scrutinize the progress of each member, publishing their findings annually. They will examine whether commitments have made the jump from promise into action.

Let's be clear: this won't be easy. Most countries would prefer to mark their own homework. But who has faith in assessments given by politicians about their own actions? To be credible the mechanism must be independent. And to be truly independent the mechanism can't be run by governments.

Britain is leading from the front - we and the partnership's other founding members will be the first countries to be examined.

To ensure that the reporting remains independent, the mechanism's work will be overseen by an Independent Expert Panel. We can announce today that three internationally respected senior advisers will sit on the Panel: former Irish President and UN High Commissioner for Human Rights Mary Robinson; the Sudanese-born entrepreneur Mo Ibrahim; and the Mozambican politician Graça Machel. It is a tribute to the growing reputation and importance of the OGP that these three have agreed to add their expertise to its work.

During the year ahead, Britain will promote the OGP and highlight the advantages of openness in government. We know transparency helps root out corruption, exposes inefficiency, and highlights incompetence.

But for transparency to strengthen the hand of democracy there is another critical element: the searchlight of a free and rigorous media. So, I renew my call for journalists the world over to shine an unforgiving light on the data that governments release. Waste, mismanagement and dishonesty should have no dark corners in which to hide. Failing hospitals, wasteful governments, corrupt officials, misguided politicians - all should be exposed. The media must help us ensure that openness sticks.

This government is second to none in opening up data. We have already released nearly 9,000 datasets, fuelling new and innovative businesses as well as apps that make everyday life easier and safer. But it's not for the government to exploit the data we are releasing. Yes we should make all the data we can available in the most user-friendly way possible. But we will never be the best judges of its potential value nor the experts at exploiting it. That's why I'm delighted that the independent Open Data Institute (ODI) will launch next week on the 4 December.

The ODI, led by Sir Tim Berners-Lee and Professor Nigel Shadbolt, will help to unleash the potential of open data, foster a new generation of innovative data-driven businesses, and challenge government to release ever more useable data. The appetite is certainly there. Research by Deloitte supported by the ODI will be published next week showing that the popularity of the UK's open data is among the highest in the world, with data.gov.uk receiving more daily visits than equivalent open data sites in the US and France.

And the potential rewards are huge - data could be worth billions across Europe alone.

The opportunities and rewards of openness the world over are enormous. Yet to realise them governments will have to change and adapt under the spotlight of transparency. We in Britain have started down this path and we are already out of our comfort zone. But there is no going back. The developments of the next week will help us take the hard steps towards that welcome point of no return.

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