"The whole world is angry because they see avoidable deaths - of children, mothers, and families affected by a disease that could have been avoided," he said.
"This is a humanitarian catastrophe. This is a breakdown in civil society. It is a blood-stained regime that is letting down its own people."
Brown said he had been in contact with African leaders "to press for stronger action to give the Zimbabwean people the government they deserve".
He also said he is hopeful that the United Nations Security Council meet to consider the situation in Zimbabwe.
Brown's statement against the Zimbabwean president comes a day after Condoleezza Rice, the US secretary of state, said that Mugabe's exit from office is overdue.
Mugabe has been president of Zimbabwe since 1980, when the country, previously known as Rhodesia, won independence from London.
Mugabe’s Zanu-PF party and the opposition Movement for Democratic Change (MDC) have in recent months failed to reach a deal over the allocation of cabinet seats.
The distribution of cabinet portfolios is the key element in forming a power-sharing government after disputed presidential and parliamentary elections earlier this year.
Zimbabwe is struggling to control the world's highest rate of inflation, while a cholera outbreak has spread to neighbouring countries as Zimbabweans seek medical treatment and food abroad.
Brown called for medical supplies to be dispatched urgently to Zimbabwe to tackle the country’s cholera outbreak.
A "command and control structure" should be put in place in the Zimbabwean capital, Harare, to co-ordinate aid efforts, he said.