Britain is to withhold £21m of aid to the government of Rwanda after accepting “compelling reports” that the country is supporting rebels in the Democratic Republic of Congo.

The move comes just three months after the former International Development Secretary, Andrew Mitchell, controversially reinstated £8m of direct budgetary support to Rwanda on his last day in the job.

Mr Mitchell, who had long-standing links to the government of President Paul Kagame, argued that he had reinstated the aid because the Rwandan government had met three conditions set down by the United Kingdom.

But his successor, Justine Greening, said today that the next payment of money, due to be paid this month, would not be released because the Kagame regime had breached the agreements.

“The Government has already set out its concerns over credible and compelling reports of Rwandan involvement with M23 in DRC,” she said. “This evidence constitutes a breach of the partnership principles set out in the Memorandum of Understanding and, as a result, I have decided not to release the next payment of budget support to Rwanda.”

Violence in DRC has been increasing, with reports of summary executions by the rebel M23 group and growing numbers of refugees.

The UK suspended the last tranche of £16m of aid in July after an interim UN report highlighted Rwanda’s role in backing the insurgents. Pressure to halt the aid payments again intensified earlier last month when UN experts presented more evidence of Rwanda’s involvement in fuelling the conflict.

Ms Greening also said today that DFID will provide a further £18m of immediate humanitarian support in the DRC, providing emergency food for 100,000 people, clean water and education.

The Prime Minister’s spokesman denied that the decision to reinstate aid in September had been a mistake.

“We stand by the decision that we made to release the last tranche of funding,” he said.

Meanwhile, the International Development Select Committee said aid to Rwanda should in future go through non-government channels.

The cross-party group of MPs also said they “did not understand” why Mr Mitchell concluded that the state was no longer supporting the M23.

“Mr Mitchell has assured us that he carried out extensive consultations within the UK Government and with the government of Rwanda before making his decision,” they said.