England players are to be banned from bringing women back to their hotel rooms after four members of the touring squad were accused of a serious sexual assault.

The Auckland police's adult sexual assault team is investigating an incident alleged to have occurred at the England hotel early last Sunday morning.

The four players have denied the allegation of rape and/or sexual assault in the "strongest terms''. They have declined to be interviewed by New Zealand police on the grounds that the woman in question has not made a formal complaint.

Even if the alleged incident passes over, the Rugby Football Union (RFU) are concerned the reputation of England and English players will be damaged.

The squad's code of conduct for the tour did not prevent players from bringing women back to the team hotel.

A new set of standards has been agreed and will come into force from July 1, when the players sign their new elite rugby contracts.

But RFU chief executive Francis Baron confirmed the issue of women being entertained by players in their hotel rooms would be addressed as a matter of urgency.

Baron said: "The code of conduct has never specifically dealt with that aspect. Talking with my colleagues in the New Zealand Rugby Union, for example, who have had incidents like this in the past, they have moved to a much more prescriptive code of conduct about women being allowed into the team hotel.

"When we get back home, we will be looking to see what measures we should put in place to protect our boys from this type of thing in the future.

"This is the first time the England rugby team has got into this position. It is distressing to everybody involved in rugby.

"In a way it makes us absolutely determined to do whatever we can to ensure such a set of circumstances never happens again for future generations of players.

"Clearly we have got to get across to these young men, who are now very high profile individuals, that they are targets for people to use.

"They have to be so careful, so conscious of what they do going forward. Working with the Premiership clubs we have to educate our young men for the realities of the new world of celebrity they face so we minimise the risk going forward of any of our young boys getting involved in an incident like this.''

A police statement said: "Auckland City Police will continue to investigate the allegation - that a woman was raped and/or sexually assaulted by four players - as thoroughly as possible before reviewing the file.

"Any decision about where to take matters from there will depend on the outcome of that review.

"While no formal statement has been made by the woman who made the allegations, a formal complaint can be made at any time in the future and police are then obliged to assess the evidential basis of that complaint.''

England's footballers exist behind a ring of security whenever they travel abroad to play.

Rugby has always had the image of being a much more sociable game, with players mixing with fans and opponents for a beer after the game, but there is now a very real danger of that changing forever.

Already, security guards have been posted in the England team hotel in Christchurch, where they are trying to prepare for tomorrow's second Test against the All Blacks.

Baron and RFU president Bob Taylor are very concerned about the damage this situation will do for rugby's image, whether anything comes from the allegation or not.

Taylor, a former England captain, said: "The game could be damaged, not just in England but worldwide by these allegations that we are seeing our players suffer.''

The RFU have hired independent lawyers for all four players, who are said to be "angry and frustrated'' at being unable to actively clear their names.

The legal advice is for the players not to answer any police questions unless the alleged victim comes forward with a formal complaint.

Baron said: "Each of the individuals has denied any wrong-doing in the strongest terms.

"There are some lurid allegations floating around. The boys have totally denied them. In our view those boys are innocent until proven otherwise.

"They have and will continue to have our full support in their efforts to clear their names as soon as possible.''

That is now dependant on a formal complaint being lodged with the police.

"I know the boys are very upset and very frustrated they can't clear their names ASAP,'' said Baron.

"It is a very difficult situation with no complaint being made. You are trying to clear yourself but against what?

"I hope I am conveying the anger and frustration those young men are currently facing. They don't know what the charges are, they don't know how they can get to where they want to be.

"There doesn't appear to be any immediate end to the process, in the absence of there being a complaint.''

The England team management have been involved in a "series of discussions and meetings with the squad's legal representatives'', according to the RFU.

If there is no change to the current situation, the England players will be free to leave New Zealand as planned on Sunday.