The UK will not nominate a European commissioner before December, Westminster announced on Thursday.
Incoming head of the European Commission, Ursula von der Leyen, has twice asked the UK to nominate someone since Brexit was delayed to January 31.
"We have written to the EU to confirm that pre-election guidance states the UK should not normally make nominations for international appointments during this period," said a UK official on Thursday.
The UK is going to the polls on December 12. The news means that current UK commissioner Julian King may be the UK's final European commissioner.
What is the European commission?
The commission, made up of von der Leyen and senior officials from 26 other members states, plans to take office from December 1. The European Commission is the executive branch of the European Union.
Von der Leyen has had legal advice that she will not be breaking the law by assembling her team without a UK commissioner.
The former German defense minister was supposed to take up the role from November 1, but has been plagued by controversy over appointments to the commission. She received a backlash after naming a new commissioner for "protecting the European way of life" and MEPs rejected her initial Hungarian, French and Romanian candidates.