Dylan Hartley is set to miss the World Cup after being dropped from England's training squad for disciplinary reasons, head coach Stuart Lancaster has announced.

The Northampton hooker was ruled out of the three warm-up games and tournament opener against Fiji on 18 September after being banned for four weeks for head-butting Saracens' Jamie George on Saturday.

"We are obviously very disappointed with the situation that Dylan has put himself in and where that leaves us as a squad. I have spoken to him and he knows he has let himself and everyone down," Lancaster said.

Hartley has now been suspended for a total of 54 weeks for a range of offences including gouging and biting.

The 29-year-old, England's most capped serving player, missed the 2013 Lions tour to Australia after being banned for abusing official Wayne Barnes during the Aviva Premiership final.

When explaining his decision, Lancaster concentrated on the selection issues surrounding the difficulty of preparing for and entering a World Cup with only two available hookers rather than Hartley's ongoing disciplinary lapses.

And the head coach has left the door open for him to make an appearance at England 2015 if injury strikes in the number two jersey. Replacement players can be called up in the event of a tournament-ending injury.

In a twist of fate, it is George who takes Hartley's place in the 50-man training squad.

"If we selected him in the World Cup squad he would have played no competitive rugby at all and we would be left exposed with only two available hookers in what is a specialised position going into the Fiji game," said Lancaster.

"All it would take is one injury during the week of the Fiji game and we would only have one fit hooker in the squad for our crucial opening game and this would leave us massively exposed.

"In addition, the regulations also clearly state that in our World Cup squad we must have sufficient cover that is suitably trained and experienced in the front row in case of injury.

"This is clearly not the case if we begin the tournament with a suspended hooker and as such we have been left with no choice but to replace him.

"It also goes without saying that we need all our players to be able to control their discipline and make good decisions under pressure, the World Cup will clearly require this, and Dylan has not displayed this in this latest incident. This is an area that he still needs to address.

"Dylan will be replaced by Jamie George in the World Cup squad and will not be considered until the suspension is served."

Hartley's disciplinary hearing was held on Wednesday night and the Northampton hooker pleaded guilty to the unprovoked assault on George.

"I'm devastated with what has happened and the position I have put myself and the England team in," Hartley said.

"I would like to apologise to Jamie, Stuart, and my team mates both at Saints as well as England. What happened is not acceptable and I understand why this decision has been made."