LABOUR has called on Theresa May not to allow another act of “cronyism” by David Cameron after the former Prime Minister’s onetime chief of staff and fellow Old Etonian Ed Llewellyn was said to be in line as the UK’s next ambassador to France.

The plea from Tom Watson came after Jean-Claude Juncker, President of the European Commission, approved Sir Julian King, the current British ambassador to Paris, as the European commissioner for security. His appointment has to be approved by MEPs.

READ MORE: SNP claim Scotland on the 'outside' of May government

However, in the wake of the row over Mr Cameron’s resignation honours list, Labour’s deputy leader called on the Prime Minister to block Mr Llewellyn’s appointment to the vacant plum diplomatic job.

“If it’s true that Ed Llewellyn is being lined up as ambassador to France, Theresa May must block his appointment,” declared Mr Watson.

“She can’t walk away from this cronyism row, which risks undermining public confidence in the honours and appointments system,” he added.

His Labour colleague, backbencher Wes Streeting also demanded “serious scrutiny” of the appointment, telling the London Evening Standard that the most suitable “heavyweight career diplomat” had to be appointed to the ambassador’s role.

READ MORE: MEP calls for referendum on the Queen if Scotland goes independent

Mrs May has made clear she will not interfere in Mr Cameron’s resignation honours list, which is said to include nearly 50 people with gongs for Tory donors, cabinet colleagues, spin doctors, Downing Street staff, former ministerial drivers and even Samantha Cameron’s personal stylist.

Asked about Mr Llewellyn’s putative appointment, a Downing Street described it as “speculation”.

Mr Llewellyn, 51, served as Mr Cameron’s chief of staff for the whole six years of his premiership.

In light of the Brexit vote, Sir Julian, also 51, had not been expected to be handed such a high profile portfolio; the UK Government has already signalled the beginning of Britain's divorce from the Brussels bloc by relinquishing the rotating EU presidency it was due to take up next year.

READ MORE: Ukip to announce runners to succeed Nigel Farage on Wednesday

Mr Juncker said security was a "pressing challenge" and the wave of terror attacks in France, Germany and Belgium had underlined the need for "swift progress".

He said Sir Julian would be expected to come up with "concrete" action to tackle terrorism, prevent radicalisation, disrupt organised crime and fight cybercrime, he added.

The new commissioner has been tasked with drawing up measures to deal with returning foreign terrorist fighters, improving information and intelligence sharing and boosting protection for critical infrastructure and soft targets.

Despite the Brexit vote, the UK remains a full member with the right to one of the 28 seats on the powerful Commission until it has formally left the EU.

Sir Julian was sent to Brussels to fill the vacancy left when former commissioner Lord Hill of Oareford resigned in the wake of the referendum result.

A career diplomat, he took up an ambassadorial posting in Paris in February this year, having previously served as ambassador to Ireland from 2009 to 2011.

Downing Street welcomed Sir Julian’s appointment, saying security was a “vital issue for all member states and co-operation across the EU can help to better protect us all from the range of threats we face”.