Calls on Mr Cameron to boycott the event risked an embarrassing split with Buckingham Palace, had the Queen travelled to the meeting as the Commonwealthâ€™s head.
The organisation decided at its last meeting two years ago to hold the Commonwealth Heads of Government Meeting (Chogm) in Sri Lanka this year but many states have since been dismayed by Sri Lanka’s failure to heed calls for reform.
In particular Colombo has come under fire for its failure to promote reconciliation with the Tamil minority in the aftermath of the vicious civil war that ended in 2010.
Officials said yesterday that Mr Cameron had decided to make a robust stand in person against Sri Lankaâ€™s human rights record and attacks on its democratic standards by its authoritarian president, Mahinda Rajapaksa.
â€œWe do not think that turning away from the problem is the best way to make progress in Sri Lanka. Thereâ€™s nothing to suggest that not going will convince Rajapaksa he must do more,â€ said a government spokesman.
â€œInstead, we should make very clear that as the incoming chair of Chogm they need to live up the values of the Commonwealth. We believe that the attendance of many world leaders and the global media will help to shine a light on what is going on the country, what has been achieved and what more needs to be done.
â€œAnd the PM will use his visit to see the situation in the country for himself and be clear on what progress is needed.â€
The Coalition has made developing ties with the Commonwealth a key plank of its foreign policy and the row threatens to undermine the body when it had been reviving. The country that hosts of Chogm goes on to serve as its chairman for the following two years.
Leading Commonwealth countries have been sharply divided by the choice of Sri Lanka as the venue for the summit.
Stephen Harper, Canadaâ€™s Conservative prime minister, has said he wonâ€™t attend and his foreign minister, John Baird, called the decision to choose Sri Lanka â€œevilâ€. Canada has demanded a credible inquiry into allegations that up to 40,000 civilians were killed by Sri Lankan troops in the final phase of its war against Tamil rebels in 2009 before the summit can take place. However Australia has condemned boycott proposals as â€œwrongâ€.
One Commonwealth diplomat has said handing Sri Lanka the lead role for two years would â€œkillâ€ the Commonwealth as a functioning diplomatic forum.
Downing Street has taken the view that it can push Mr Rajapaksa in the coming months to adopt recommendations of its own reconciliation inquiry into the Tamil conflict.
It also hopes that the government will allow free provincial elections in September.
â€œThe prime minister believes this is the right thing to do for the Commonwealth and he will take a very tough message to the Sri Lankan Government: that they need to make concrete progress on human rights, reconciliation and political settlement,â€ the official said. â€œThis Government is a strong supporter of the Commonwealth and we firmly believe that it can continue to be a force for good around the world, promoting the important values about freedom and democracy and rights.â€ (The Telegraph)