Felix Jones' resignation as England defence coach after only seven months is "deeply disappointing", Rugby Football Union chief executive Bill Sweeney said as he confirmed the Irishman's departure.

Jones, 37, joined the set-up after securing a second successive Rugby World Cup with South Africa last autumn.

He overhauled England's defence, introducing a Springbok-style blitz approach.

England conceded 13 tries in the 2024 Six Nations, compared to 18 in the same tournament a year earlier.

Sweeney said the RFU are looking to move on after Jones' resignation "came out of the blue".

"Felix is on a 12-month contract so from the moment he announced his resignation he is committed to us for 12 months," Sweeney told BBC Radio 5 Live.

"We are in discussion about what we do in that transition period.

"It has been deeply disappointing and I won't beat any bones about that. You saw with the performances in New Zealand and at the end of the Six Nations great momentum and good energy.

"You have a great squad of players now with a blend of experience and young players. The mood in the camp is great and its a fun environment to be in.

"It was totally unexpected but these things happen in sport and we will move on and make the necessary changes to rectify it."

Jones' exit adds to the vacancies among head coach Steve Borthwick's backroom staff with head of strength and conditioning Aled Walters and department colleague Tom Tombleson also leaving this summer.

Doubts remain over Kevin Sinfield's future. The rugby league great was initially recruited on a five-year contract as defence coach after working with Borthwick at Leicester Tigers.

However the 43-year-old shifted into a skills role less than a year later and had originally planned to step down this summer, with Borthwick having previously suggested he may still have a role to play in a part-time capacity.

Sweeney says it is too "early" to make any announcements.

"Some of the decisions that have to be taken may take a bit of time," he added.

"People are under contract but we are working really hard on it and we have had to accelerate our thinking on that."

Northampton's defence coach Lee Radford and former Bristol flanker Joe El-Abd, who is head coach of French side Oyonnax, are reportedly among the names under consideration.