The UK government on Thursday prolonged a freeze on its international aid budget introduced during the pandemic in a move condemned by charities.

Boris Johnson's administration in 2020 cut the annual budget for overseas development aid from 0.7 to 0.5 percent of gross national income (GNI), breaking an election promise.

Finance minister Jeremy Hunt said while unveiling his austerity budget Thursday that it "will not be possible to return to the 0.7 percent target until the fiscal situation allows".

He said the government remained "fully committed to the target" but he was assuming spending would "remain around 0.5 percent for the forecast period" over the next five years.

Christian Aid slammed the decision, with chief of UK advocacy Sophie Powell saying Hunt had "chosen to balance the books on the back of people in poverty".

The move comes as the government uses part of the overseas aid budget to support refugees at home.

The CEO of World Vision UK charity, Mark Sheard, tweeted Thursday that the government is "making real terms aid cuts" and "pulling back its support when more is desperately needed".

Opposition Labour MP Kate Osamor tweeted "this cut will kill" and "vital programmes that save lives and lift people out of poverty will be closed".

Parliament's International Development Committee on Wednesday announced an inquiry into whether using the Official Development Assistance budget on refugees within the UK was "an efficient, effective and ethical use of public money".

Conservative MP David Davis told Sky News Tuesday that a "good chunk of (the aid budget) is being used to deal with the problems the Home Office has with migrants".

He suggested the figure being spent overseas was only about 0.3 percent.

"Not many things in the budget are going to kill people but this is an element where I think we have to bite our lip and do something about it," he said.

Johnson blamed the original 2020 cut on ballooning debt caused by the Covid pandemic.

Announced as a temporary measure, it broke a legally enshrined commitment on aid to poorer countries.

In October last year, then-finance minister Rishi Sunak, who is now prime minister, promised the 0.7 percent rate would be restored in 2024 or 2025 given the right fiscal circumstances.