The concerns over Brexit financial implications have been well documented, but Britain's exit from the European Union could blow a €20bn ($23bn, £17.6bn) hole in the bloc's budget.

Günther Oettinger, the European commissioner for the budget, warned the EU might have to adopt drastic measures to fill the gap. Oettinger went as far as suggesting additional taxes might have to be introduced, while the EU might have to reassess its ambition by March 2019.

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"We won't have the UK with us any more, but they were net payers despite the [former British Prime Minister Margaret] Thatcher rebate, so we will have a gap of €10bn-€11bn a year," he said.

Britain receives over €3bn a year in the shape of a rebate for its budget contribution. Germany, Sweden, Austria and the Netherlands also received money back as part of that agreement, which was struck by Margaret Thatcher's government.

However, writing on a separate blog, the German official indicated the need to finance new initiatives in a number of sectors, such as security and defence, meant "the total gap could therefore be up to twice as much".

The 28-country bloc's budget this year stood at €157.9bn and the EU has indicated it intends to soften the blow of Britain leaving by holding the UK government to fulfill the commitments it made before Brexit.

Additionally, a study on the future of the EU budget warned that with Britain leaving the bloc, the rebate might become obsolete.

"With the departure of the United Kingdom, the rebate that was introduced as a concession to that country in the past will become obsolete," said the paper, which was published on Wednesday (29 June).

"The same is true for the rebates on the UK rebate. The other rebates will expire at the end of 2020. The elimination of rebates would open the door to substantial simplification of the revenue system."

The report added that should Europe being unable to deliver on its current policies with a reduced budget, it could either scaled back its ambitions or bridge the gap left by the UK by increasing contribution from the remaining states or from external sources of revenue.

Whatever the outcome, the level of political ambition must be aligned with the means," it concluded.