Shadow foreign secretary Douglas Alexander has said Prime Minister David Cameron must "urgently consider reversing his decision" to attend the Commonwealth Heads of Government summit in Sri Lanka this week.
"For months Labour has urged the Government to do more to raise Britain's concern over human rights in Sri Lanka in the run up to the summit," Mr Alexander said.
"If the Prime Minister now chose to reverse his decision to attend the summit - even at this late stage - he would have Labour's full support."
The Prime Minister's historic visit to northern Sri Lanka highlighted human rights issues at the start of the Commonwealth summit.
A press conference due to be held today with Sri Lankan President Mahina Rajapaksa was cancelled at the last minute.
Democratic freedoms are being clipped and police vans are waiting for those who might disagree what the Sri Lankan government is doing.