• Harlequins’ John Kingston says 18-year-old must not be used in Six Nations • ‘He is a way off being someone to play international rugby’

Eddie Jones has been urged to resist any temptation to hand Marcus Smith a first England cap during the Six Nations by the Harlequins director of rugby, John Kingston, after the teenage fly-half orchestrated his side’s 50-21 thrashing of Northampton.

The 18-year-old had a hand in five of Quins’ seven tries here on his 11th Premiership appearance, in front of the watching Jones. On Friday, Smith was selected for England’s training camp in Brighton but again as an “apprentice” player, along with Bath’s Zach Mercer.

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Smith was an ever-present in the England squad during the autumn internationals but Jones was insistent that he would not be considered for selection. He also suggested in September that Smith can be his “X-factor rookie” for the 2019 World Cup, but Kingston has urged caution, revealing he intends to rest the youngster when Demetri Catrakilis and Tim Swiel are fit again.

“Eddie’s decision to have him involved in the group – that’s fine, that’s up to him – but he is a way off being someone to play international rugby,” said Kingston. “I am a great believer that you come into an international set-up when you are good enough to play 50 times for your country, not get one game and thrown back because it was not the right thing.

“Let’s just calm down and let him progress the way he is. Eddie Jones knows his job so let him get on with his job and I will get on with mine.

He [Smith] is a fine rugby player and was pulling the strings. We have to make sure we take it stage by stage. He has probably had more rugby than we would have thought was right with Demetri and Tim out. We are managing him pretty well even though he is probably playing a bit more rugby than we would have thought.”