Foreign Secretary Boris Johnson has spoken of witnessing "sheer devastation" during a visit to northern Rakhine state in Burma - where minority Rohingya Muslims have fled in recent months.
Around 700,000 Rohingya fled to neighbouring Bangladesh following ethnic violence in Burma with troops accused of widespread abuses.
Mr Johnson said he spoke to de facto Burmese leader Aung San Suu Kyi about the situation - but cast doubt that she understood "the full horror" of what had happened.
He said: "I don't think it has come through to her the full extent, the horror of what has happened, the sheer devastation.
"I don't know whether you've ever seen anything like it done by mankind against our fellow man. I've seen nothing like it in my life.
"Hundreds, hundreds of villages torched. It's absolutely devastating and I think that what is needed now is some leadership, some calm, but some leadership working with the UN agencies to get these people back home."
Mr Johnson added villagers were so frightened, they could not say who had burned their homes.
He said: "We had this farcical account that villagers themselves had set light to their homes. The villagers themselves thought that was absurd.
"I believe she (Ms Suu Kyi) can still make a change and make a difference, but to do that she needs to get the agencies in, get the refugees back home in a way that is safe and voluntary and dignified."
Speaking after meeting Ms Suu Kyi, he said: "The UK is already a major donor to the humanitarian crisis. We will continue to use all our diplomatic tools and influence on the global stage to find a way to provide a better future for the Rohingya community.
"I encouraged her efforts to broker a nationwide peace settlement to put to an end 70 years of conflict in her homeland."