David Cameron has rebuked other European leaders for their attempt to "ambush" him and dilute the rebate the United Kingdom receives from the EU.
Speaking in Brussels the prime minister said he came to the summit prepared to "lock and load and have one up the spout" in order to defend the money.
Britain gets £3.1bn back from Brussels each year to compensate it for the lower amount of agricultural and infrastructure funds it gets compared to other member states.
Cameron told a press conference on Friday morning: "The rebate is fair right and I will not allow changes that weaken or undermine the rebate in any way.
"It is frankly not acceptable for it to be left to the last minute and then an attempt at reopening it, and an ambush at 1am at the end of a European Council meeting. I think this is no way for an organisation to conduct itself."
He added: "I am frustrated I have to go through that battle all over again. But in this town you have to be ready for an ambush at any time, and that means lock and load and have one up the spout, and be ready for it."
The prime minister, however tempted, refused to be drawn on which other European countries had wanted to cut the rebate.
But it is known that France has been trying to reallocate 10% of the rebate for farming subsidies for new EU member states.
On Thursday EU leaders secured agreement on a budget for the union of of £852bn - overcoming opposition from the European Parliament.