"Under no condition can we agree with this logic," European Council President Donald Tusk said.
Tusk's comments follow the British prime minister's accusations that Brussels was meddling in the U.K.'s election.
Nation says it will obstruct business in Brussels as payback after the bloc supported Donald Tusk's leadership of the European Council.
British chancellor George Osborne has stressed the finality of the upcoming referendum vote.
EU leaders agree to triple naval search mission in Mediterranean following drowning of 900 people in past week.
The controversial food stuff made it on to the menu despite many farms falling short of EU standards
Poland's new Prime Minister Ewa Kopacz must focus on internal leadership struggles, say leading party figures