The players caught up in sex allegations in New Zealand could return to England and spend the rest of their lives under threat of being charged, a leading legal source yesterday told the Guardian. "For indictable offences such as this, there remains the scope for police to charge someone if evidence suddenly emerges 10, 20, 30 years in the future," said the source. "The case will never fully close."

Because of the serious nature of the accusation, there is no time restriction on the case, meaning the investigation will only be suspended if the alleged victim drops the claim or police find enough evidence to prove it was false in the first place, he added.

Another legal expert, Scott Optican, an associate professor at Auckland University's faculty of law, confirmed that unless police came up with enough evidence to lay charges, the players would be free to leave the country as scheduled tomorrow after the second Test. If a player were charged, he could be detained or he could be given bail and agree to return for trial. Optican said if the players did leave and the police were to continue to gather evidence, there was a possibility that they could ask English police to arrest any suspect and that they could then either return voluntarily or be extradited.

"New Zealand's legal system is exactly the same as England's in that a person is free to go about his or her business - and that includes leaving the country - up until they are arrested. The only power police have to detain a person is to arrest them and they can only do that if there are reasonable grounds to suspect a crime has been committed. The police therefore have the burden to prove they have enough of a case," Optican said.

The players were said to be "angry and frustrated" and desperate to prove their innocence, according to Rugby Football Union officials. The union is also concerned that players' families are suffering unnecessarily while Auckland police still await a formal complaint by a woman who was allegedly raped or sexually assaulted in the squad's hotel last Sunday.

Francis Baron, the RFU's chief executive, said yesterday that he and the team were unhappy at the prospect of flying home with the case ongoing and suggested the current state of limbo was "unfair" on the four individuals concerned. "We have to give these young lads every opportunity to clear their names," insisted Baron.

"It is in everybody's interests to do it as quickly as possible. I know the boys are very upset and frustrated. They don't know what the charges are, and they don't know how they can get to a situation where their names can be cleared. In the absence of a complaint there appears to be no immediate end to this process."

On Wednesday night the players, via their legal representatives, had declined to answer questions relating to the alleged incident. Police said they would continue their inquiries and their spokeswoman Noreen Hegarty added: "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."

Baron said players' families were being placed under intolerable pressure by the speculation. "We are hearing reports of mothers being approached. That's why it's so important to bring closure to this incident. It is affecting other people and there is uncertainty out there as to who is or is not involved.

"If a complaint is not made in the next two to three days I'm sure our legal team will be pressing police to close the file because it is a very unusual situation.

No complaint has been made and the damage to the individuals is very substantial. That is unfair under any jurisdiction. There are some lurid allegations floating around [but] the boys have totally denied them. In our view those boys are innocent. Until proven otherwise they're innocent and will continue to have our full support."

Unconfirmed reports say the players had been part of a drinking session at the Pony Club bar in Auckland on Saturday night where they were accompanied by several women. The players returned to their hotel where one 18-year-old is said to have had sex with two players, witnessed in part by two other players. After the woman returned home a subsequent allegation of a sexual nature was made.

New Zealand v England

AMI Stadium, Christchurch Today, 8.35am BST

Referee J Kaplan (South Africa)

15 MacDonald Canterbury

14 Sivivatu Waikato

13 Kahui Waikato

12 Nonu Wellington

11 Wulf North Harbour

10 Carter Canterbury

9 Ellis Canterbury

1 Tialata Wellington

2 Hore Taranaki

3 Somerville Canterbury

4 Thorn Tasman

5 Williams Tasman

6 Thomson Otago

7 McCaw Canterbury, capt

8 So'oialo Wellington

Replacements Mealamu (Auckland), Woodcock, Boric (both North Harbour), Lauaki (Waikato), Cowan (Southland), Donald (Canterbury), Muliaina (Waikato).

15 Tait Newcastle

14 Ojo London Irish

13 Tindall Gloucester

12 Noon Newcastle

11 Varndell Leicester

10 Flood Newcastle

9 Care Harlequins

1 Payne London Wasps

2 Mears Bath

3 Stevens Bath

4 Palmer London Wasps

5 Borthwick Bath, capt

6 Haskell London Wasps

7 Rees London Wasps

8 Narraway Gloucester

Replacements Paice (London Irish), Hobson (Bristol), Kay (Leicester), Worsley (Wasps), Richards (London Irish), Barkley (Bath), Strettle (Harlequins).