A week from now I will arrive in Colombo to join leaders and representatives from 52 other Commonwealth member states for our biennial meeting. Today in Downing Street I will meet Tamil representatives from communities here in Britain to discuss their concerns about the situation in Sri Lanka and to hear the messages they want me to take to the government there.

Some, including many in the Tamil community here in Britain, have called for me not to attend because of the Sri Lankan government’s poor record on human rights and cruel treatment of Tamils. Four years after the conflict no one has been held to account for grave allegations of war crimes and sexual violence, journalists are routinely intimidated and thousands of people have yet to find out what has happened to their missing relatives. 

I want to see that change. And I do not believe boycotting the Commonwealth meeting will achieve that. The right thing to do is to engage. To visit the country. To shine the international spotlight on the lack of progress in the country. And to have frank conversations with the Sri Lankan government about what they must do to address the concerns of the international community and to improve the daily life of thousands of Tamils and civilians across all communities.

I will visit the north of the country – the first leader to do so since Sri Lankan independence in 1948 – precisely so that I can see the situation on the ground with my own eyes and meet people directly affected by the conflict.

Recent progress on elections, reconstruction, demining and resettlement of those displaced by the conflict is important but it is frankly not enough. I will demand that the Sri Lankan government independently and transparently investigates alleged war crimes and allegations of continuing human rights abuses; guarantees freedom of expression; and stamps out intimidation of journalists and human rights defenders - including by bringing those responsible to justice.

This will not be an easy conversation. But diplomacy is not about ducking the difficult discussions. It is about talking to those that you may not agree with precisely because you want to change their approach.

We must also not forget that this meeting is not only about Sri Lanka, the host of this year’s meeting – a decision agreed in 2009 under the previous Government. 

The Commonwealth represents 2 billion people - nearly a third of our world’s population - and some of its fastest growing economies. And we want it to remain a force for good in the world, promoting democracy and human rights and creating new opportunities for prosperity among its 53 member states.

This requires all the Commonwealth’s members to value the organisation, to participate fully in its discussions and work closely together.

And finally, if we are not at the table we have no way of encouraging the Commonwealth to take a strong stand on issues that we care about deeply in our country. We want to ensure that the international framework that succeeds the Millennium development Goals has the rule of law and good governance at its heart. We want to promote freer and fairer trade. These things matter to Britain – to our security and to our prosperity – and I am determined to be present to argue for them.

For these reasons attending the summit is not a betrayal of Britain’s values or the Tamil people, it is the way we champion them.

We want the Commonwealth to take action on the things that matter to the UK and we will not achieve that by sitting on the sidelines.