The EU insisted Friday that member states must find more than two billion euros this year to cover spending on Ukraine and youth unemployment projects after Britain baulked at the demand.
"We put the draft amending budget (for 2014) on the table because member states have taken important decisions that concern the whole of Europe," a Commission spokesman said
"These decisions must now be covered," the spokesman said.
The Commission said Wednesday it needed some 4.7 billion euros ($6.4 billion) to cover a series of projects, among them extra support for small- and medium-sized businesses, new member states, and for Ukraine.
After including other sources of funding, the net amount comes down to 2.17 billion euros, but the request has still been called unacceptable by Britain, where the government has been rocked by the stunning success of the anti-EU UK Independence Party in last week's local and European elections.
"At a time when countries across Europe continue to take difficult decisions to deal with deficits, the European Commission should not be asking Europe's taxpayers for yet more money," a spokesman for the British Treasury said.
"(The) EU should manage any additional spending pressures through the reallocation of existing funds within the agreed budget," he said.
"We will work with other governments to achieve a budget for this year which ensures budget discipline and reflects the economic reality in Europe," he added.
In response, the Commission spokesman said: "It is fine if member states make statements but at the end of the day... we try to bring their positions together."
British Prime Minister David Cameron led the charge in negotiations on the European Union's 2014-20 budget, winning last year a first ever real cut of 3.5 percent in the nearly 1.0 trillion euros spending programme compared with 2007-13.
Spending for this year was initially set at about 135 billion euros, down about 7.0 percent from the previous year.