Theresa May has strongly defended British taxpayer-funded cash handouts to people in Pakistan after a senior Tory MP called for a review of the programme which he compared with "exporting the dole".
Downing Street said the scheme was helping the poorest families in Pakistan and was an efficient and effective way to make sure they had the support they need.
The UK aid budget helps fund the Benazir Income Support Programme (BISP), which offers cash amounting to just over £10 a month to some of the poorest families in a country where 60 million people live on less than £1 a day.
A spokeswoman for the PM told a Westminster briefing that there were "robust" systems in place to protect against corruption and fraud.
"These are cash transfers that are focused on making sure that aid is targeted at those who need it, when they need it. The effectiveness of such transfer schemes has been recognised by the Public Accounts Committee and the National Audit Office who have spoken about the clear, immediate benefits of this system.
"In the last four years cash transfers supported by UK aid have helped almost nine million of the world's poorest people to buy food, medicine, and clean water.
"There are robust systems in place to make sure that they are not being exploited for fraud and corruption.
"We think it is a respected system for getting aid to those that need it most. We would only pursue such an option where we were clear that results had already been achieved and verified. So, for example in the case of Pakistan, the programme there, we are providing a small contribution to a much bigger programme run by the government of Pakistan, where there are already proven results.
"There are robust systems in place to protect our aid investments. One of the things that is being introduced at the moment is making sure there are more biometric payment systems to make it one of the most secure programmes in the world.
"The Prime Minister has made it clear that our aid budget is an investment in our security and national interest, and that it is right to honour the commitments that we have made."
But MP Nigel Evans, a former Commons deputy speaker and member of the International Development Select Committee, warned that cash transfers were "clearly open to fraud".
UK backing for the Pakistan government's BISP led to cash support for over 235,000 families across the country in 2012, which could potentially increase to 441,000 families by 2020.
Officials believe that offering cash directly to those people cuts out any middlemen, reducing the risk of fraud and minimising the cost of the programme, which is helping around 5.2 million families overall.
It also means that the recipients can decide to spend the money on their most urgent needs, such as food, rent, education or medicine.
The budget for cash transfers has risen from £53 million in 2005 to an annual average of £219 million in the period 2011-15, the Daily Mail reported, with £300 million committed to the BISP from 2012 to 2020.
The newspaper investigation into the Pakistan aid scheme found people in a village on the outskirts of Peshawar taking out money from cashpoints with cards they said they had been given after paying kickbacks to officials.
But Mr Evans called on International Development Secretary Priti Patel to urgently examine the use of cash transfers.
He said: "Normally this sort of aid is only given in a crisis or emergency when it is the only way to give help.
"It only should be a temporary measure, but it seems like we're exporting the dole to Pakistan, which is clearly not a clever idea.
"Anything that involves money needs to be properly scrutinised and is clearly open to fraud with money siphoned away when it ought to be directed to those most in need.
"This is something that International Development Secretary Priti Patel needs to look at urgently to ensure that there is proper accounting for how this money is being delivered."
Ukip spokeswoman on international development, Lisa Duffy, said: "It is impossible to justify that over the last five years over £1 billion of our foreign aid budget has been given away in cash. This is just one example of where UK taxpayers' money is not being used wisely. We in Ukip are calling for the foreign aid budget to be reduced by £9 billion, freeing up resources for the priorities of the British people such as adult social care.
"The foreign aid budget should be spent on prioritising emergency aid, health and inoculation programmes and initiatives that provide sanitation and clean water.
"Surely common sense tells us that giving cash handouts in a country that has its own nuclear weapons and space programmes is simply wrong. Our own UK taxpayers are facing more and more cuts on a daily basis whilst we are providing benefits to the citizens of Pakistan.
"It is time our Government became more accountable with our foreign aid budget and started working towards free and fair trade by opening up Britain's huge consumer markets.
"That is the best path to prosperity for the world's poorest people."