Nigeria’s President Muhammadu Buhari has vowed “severe punishment” for officials who embarrassed the government by doctoring the record $31bn (£20.8bn) national budget he tabled in parliament in December.

“I have been a military governor, petroleum minister, military head of state and headed the Petroleum Trust Fund. Never had I heard the words ‘budget padding’,” Mr Buhari said in a statement.

He added that Minister of Budget and National Planning, Udo Udoma, had worked so hard on the budget that he “became almost half his size during the time”, only for “some people to pad it”.

“It is very embarrassing and disappointing. We will not allow those who did it to go unpunished,” President Buhari said.

Changes to the budget – the first presented by Mr Buhari since he took office – were discovered by journalists and lawmakers when it was debated in parliament, fueling speculation that corrupt officials were behind the move.

This included a sum of $50m which was “smuggled” into the budget of the ministry of education, while Health Minister Issac Odewale disowned what was presented to the parliament, saying some “rats” had added items into his budget.