Foreign Office minister Mark Field has urged Aung San Suu Kyi to do all she can to end the suffering of the Rohingya people on a visit to Myanmar.
He told the country’s de facto leader the authorities must heed the UN’s call for violence in Rakhine to end and grant full humanitarian access.
Progress in the country risked being “derailed” by the “tragedy”, he said.
More than 400,000 Rohingya have fled across the border to Bangladesh amid reports of military atrocities.
Ms Suu Kyi, the former political prisoner who has been Myanmar’s civilian leader since winning elections in 2015, is under growing international pressure over her handling of the crisis.
In a speech on Tuesday, the Nobel Prize winner condemned human rights abuses but did not blame the army or address allegations of ethnic cleansing.
After face-to-face talks in the capital Naypyidaw, Mr Field – the first foreign minister from outside the region to meet Ms Suu Kyi since the crisis began – said he had conveyed the UK’s government dismay at events.
“What we have seen in Rakhine in the past few weeks is an absolute and unacceptable tragedy,” he said. “We need the violence to stop and all those who have fled to be able to return to their homes quickly and safely.
“During my meetings with Aung San Suu Kyi and others, I strongly emphasised the need for Burma to heed the security council’s call to end violence and allow humanitarian access to those in need of aid.”
The minister, who will visit Bangladesh on Thursday to see the relief effort in the country, said he had seen with his own eyes the damage done.
“Burma has taken great strides forward in recent years. But the ongoing violence and humanitarian crisis in Rakhine risks derailing that progress,” he added.
Speaking earlier on Wednesday, Labour leader Jeremy Corbyn appealed to Ms Suu Kyi, as a “champion of democracy and human rights”, to act now to put a stop to the violence.
“The Rohingya have suffered for too long,” he told activists at his party’s conference.
A stateless mostly Muslim minority in Buddhist-majority Rakhine, the Rohingya have long experienced persecution.
The army launched an operation in Rakhine last month after deadly attacks on police stations, which it blamed on militants. Myanmar’s military has repeatedly denied targeting civilians but witnesses, refugees and journalists have contested this.