Spending on overseas development has repeatedly risen under the controversial target of spending 0.7 per cent of national income.
But after growth forecasts were cut, the aid budget will also be trimmed.
Labour leader Jeremy Corbyn has called on the Prime Minister to increase foreign aid spending despite the economic slowdown which has seen growth forecasts slashed
But now the Labour leader has raised concerns that aid officials are not being given enough money to hand out.
In a letter to the Prime Minister, Mr Corbyn questioned an announcement in the Budget that the aid ministry will be told to tighten its belt for the first time in four years.
The foreign aid budget will be slashed by nearly £900m over two years as worsening economic growth forecasts mean the UK will be able to spend less cash to meet the controversial target.
Under David Cameron’s foreign aid law, the country must spend 0.7 per cent of national income on overseas development.
Mr Corbyn wrote: ‘As the OBR (Office for Budget Responsibility) revised growth figures down, the UK will now be spending £895 million less than expected on the intended objective of aid which is poverty reduction and tackling disease.
‘Are you confident that the Department for International Development (Dfid) has the resources it needs to deliver global development?’
Last night, Labour sources insisted that party policy remained to spend 0.7 per cent of national income on foreign aid.
Mr Corbyn’s concerns came in a letter raising the issue of a £12million foreign aid project that has been suspended amid fears some of the money has gone to jihadis.
Last month’s budget showed foreign aid spending will reduce by £375m in 2018-19 and £520m in 2019-20 due to the latest poor economic growth figures from the OBR
He wrote: ‘The British public is extremely proud of our country’s commitment to spend 0.7 per cent of national income on aid to reduce global poverty.
‘Under a Labour government, the UK was a world leader in aid effectiveness and global development.
‘Therefore, allegations of aid money ending up in the hands of an Al Qaeda affiliate and contributing to the Free Syrian Police’s work with a judicial system accused of numerous human rights abuses is yet another blow to Britain’s reputation on the world stage.’
Small print included with the Budget last month revealed that projected foreign aid spending will be adjusted down by £375million in 2018‑19 and £520million in 2019‑20.
The Department for International Development, which spends most but not all of the aid money, will have its departmental budget cut. The aid ministry has repeatedly been handed more and more cash as other Whitehall departments have been forced to make cuts.
However, Treasury documents released with the Budget show that in 2019/20, its annual funding will go down from £11.9bn to £11.7bn.
At the time of the last Budget in March, Dfid spending had been projected to go up from £12.3billion in 2018/19 to a whopping £12.6billion in 2019/20.
Ministers have been under pressure to improve how aid money is spent following Theresa May’s announcement during the general election campaign that the government would keep the controversial 0.7 per cent spending target.
Official figures released last month showed the country’s aid spending reached £13.4billion in 2016, up £1.3billion on the year before.
The chunk of the money funnelled through the EU rose by £177million to £1.5billion, despite warnings from Priti Patel when she was international development secretary about how we ‘don’t have any oversight’ over how Brussels distributed the money.
EU-run aid projects include providing juggling lessons in Tanzania and promoting African dancing.
Despite pledges to stop aid to India, last year £92.6million was spent by Whitehall officials on projects there. The amount sent to China jumped by £2.6million to £46.9million.
UK-funded schemes included £86,616 on testing whether yoga helps people who have had heart attacks in India, and £100,000 on bringing female scientists from the country to visit Cambridge University.
In China, British aid cash went on improving dementia care in Qingdao and a schools programme to encourage children to consume less salt.
Other schemes funded by the UK last year included £116,631 for the conservation of freshwater eels in the Cagayan River in the Philippines and 52,125 to promote the long-term survival of marine turtle populations in Madagascar.