BRUSSELS- Busy with a Brexit-focused election campaign, Britain will not nominate a representative for the new European Union executive until after its Dec. 12 vote, leaving the bloc seeking to hedge against any legal challenges arising from going without London.

A British official said late on Wednesday that London would not pick a name until a new government is formed. This is problematic for the bloc, which wants to launch its powerful new executive European Commission under the leadership of German conservative Ursula von der Leyen as of Dec. 1.

"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," the British official said.

Britain's exit from the EU has already thrice been postponed and the country is now due to leave on Jan. 31, 2020. For the moment, it remains a full member of a 28-country bloc where the Commission is normally comprised of one person per member state.

A spokeswoman for von der Leyen on Thursday confirmed receiving letter from Prime Minister Boris Johnson's government, which has been disinclined to name a new EU commissioner given its intent to leave the bloc.

"The UK recognises its obligations as a member state and states clearly that it does not wish to stop the EU from proceeding with the formation of a new Commission," said the spokeswoman, Dana Spinant. "The aim of President-elect von der Leyen remains to... take office on 1 December."

The snag caused by Britain's refusal to name a commissioner could be overcome with a decision by the other 27 EU states not to apply current rules, but risks of legal challenges remain.

At some point later on, Britain could even face a legal challenge from the bloc for failing to name a commissioner for the body the powers of which include negotiating international trade deals, policing members states' finances and proposing EU-wide laws on a range of topics from environment to migration.

Von der Leyen was supposed to take office at the beginning of November, but EU lawmakers' rejection of commissioner candidates from France, Hungary and Romania have held things up.

New candidates from the three countries were holding confirmative hearings in the EU parliament on Thursday.

Oliver Varhelyi, Hungary's new choice for the post of commissioner overseeing EU enlargement policy and relations with neighbours from Turkey to the Balkan countries, is "fit for the job", the largest parliamentary faction, the centre-right European People's Party (EPP), declared after his hearing.

If Varhelyi, as well as France's Thierry Breton and Romania's Adina Valean are all approved on Thursday, von der Leyen will go into a final confirmatory vote in the EU parliament for the whole of her new Commission on Nov.27.

(Editing by Mark Heinrich) ((Francesco.Guarascio@thomsonreuters.com; @fraguarascio; +32 2 287 68 17;))