The president of the European Commission has warned the remaining 27 European Union members that they will have to pay more to fill the €13bn (£11.5bn) hole Britain will leave in the bloc's annual budget after Brexit.

Speaking in Brussels, Jean-Claude Juncker urged EU countries to be ambitious and increase the amount of funds they commit to the EU budget. Once Britain leaves the bloc in March 2019, a transitional period likely to last until 31 December 2020 will be implemented to allow the remaining members to establish a new financial framework.

However, by the end of the transitional period, the EU will in all likelihood be left with an annual structural spending gap of €12bn-€13bn.

Juncker added he hoped that by May, EU states will have agreed to a proposal to spend more than 1% of GDP on the EU budget.

The 63-year-old underlined increased spending was of paramount importance to maintain the majority of current programmes and tackle future challenges, such as climate change and terrorism.

"It is difficult when a net contributor leaves the budget coffers of Europe," he said. "I'm not at all in favour of Europe becoming the place where it is free beer for everybody without having checked first what exactly one is funding."

"But I am very much in favour of looking very closely at all policies. What we need has to stay, has to be funded. It costs the European taxpayer one cup of coffee a day, that's all. And I think Europe is [worth] more than one cup of coffee a day."

The European commission has previously stated that the funding hole left by Britain can be covered by a 50:50 combination of increased spending and by implementing cuts elsewhere.

Günther Oettinger, the German budget commissioner, echoed Juncker's thoughts, suggesting EU countries should commit to spend 1.1% of GDP in funding.

"I know 50% fresh money is too much for some of you," he said at the same event. "For others, [it] is not enough. But at the end of the day, we all have to agree together. We need to get 27 governments on board [...] parliaments at a national level. They all have to agree.

"Everybody has to be ready to strike a compromise. If you just have a rigid position of your own, we will not be capable of reaching agreement. Once the Brits have sadly left then I think it will be a sign of good governance to act and do this."

Meanwhile, Juncker also dismissed the prospect of Britain backtracking on its Brexit pledge. A BMG poll showed 51% of Britons supported remaining in the EU, as opposed to 41% who were in favour of Brexit, but the European commission president insisted Britain would leave the EU by March 2019.

"There is going to be Brexit, of course," he added. "Don't believe those who say that it's not going to happen and that people have realised their error in the UK. I don't think that is going to be the case.

"My working hypothesis is that the British are going to be leaving us on 30 March 2019. So between now and then, we need to do our utmost to fund the means to react to the loss of a significant number of billions of euros."