Anti-poverty campaigners and MPs demanded to know today why £1.85 million of foreign aid funding was spent on the Pope's recent visit to Britain.
An influential Commons committee called on ministers to explain their decision to divert the money to subsidise the trip which is estimated to have cost the taxpayer £10m.
The committee also queried whether it met global aid rules.
The transfer of the funds from the Department for International Development (DFID) to the Foreign Office was discovered after an investigation into the former's accounts.
Malcolm Bruce, who chairs the international development select committee, said: "Many people will be as surprised as we were to discover that UK aid money was used to fund the Pope's visit last year," he said.
"Ministers need to explain exactly what this was spent on and how it tallies with our commitments on overseas aid."
A spokesman for the department said: "DFID was one of a number of government departments part-funding the Pope's visit to the UK.
"Our contribution recognised the Catholic Church's role as a major provider of health and education services in developing countries."
He said the money did "not constitute official development assistance" and was additional to the coalition's commitment to meet the 0.7 per cent UN aid target from 2013.
Campaigns and policy director at the anti-poverty charity War on Want Ruth Tanner said: "The government needs to tackle the root causes of global poverty. Eyebrows will be raised that ministers spent almost £2m on the Pope's visit."