no i dont see any guidline

I don't know  of any type of guidelines in place.  What specifically are you looking to address?

In my (albeit only 4 years) experience as a mentor to student nurses in the UK, I feel it is vital for the mentor to encourage professional behaviour and challenge concerning or unprofessional behaviour. And most importantly not be afraid to refer/fail students we have concerns about, obviously after the formal processes with the university and providing support and action plans to help as much as possible.

Kathleen Duffy has written extensively on issues regarding mentoring. 

The RCN provides a good handbook at http://www.rcn.org.uk/__data/assets/pdf_file/0008/78677/002797.pdf

Key influences on the professional socialisation and practice of students undertaking different preregistration nurse education programmes in the United Kingdom

International Journal of Nursing Studies, Volume 33, Issue 5, Pages 506-518

Joanne M. Fitzpatrick, Alison E. While, Julia D. Roberts

http://www.sciencedirect.com/science/article/pii/S0020748998000558

I don´t know of any guidelines.

In my experience is very important to help the student in their learning. I believe that the relationship established is essential in learning between student and tutor.

The tutor should help the student to professsional and emotional level. The established relationship provides a better integration and student satisfaction.

I don't know of published guidelines either, to add, but I would encourage you to look at the John Harftord foundation, NYU website for clinical placement guidelines with students. you may find something there of use.

I have not seen any formalized standalone guidelines established in the literature, and yet every clinical faculty at one point or another has dealt with this issue.  Much of the literature is focused on the experience of being a mentor or the student rather than how to incent experienced nurses to become mentors. The need for experienced mentors continues to be a challenge, particularly as host environments experience increasing levels of staff fatigue and increased competition for nurse mentors. Recent work in Saskatchewan, Canada has reviewed this issue and they are working on an organizational approach.  The Canadian Schools of Nursing (CASN) is offering a certificate in clinical supervision and this is a topic in that program.  My best advice would be to contact CASN directly and see if they have any documented evidence or established guidance for you.

Use search keywords nurse internship, nurse retention; I think the American Nurses Association (ANA) has published on this topic. Some of the specialty organizations such as Medical Surgical Nurses Association, Oncology Nursing Society and Critical Care Nurses Association have formal programs to assist the new graduate nurse to transition from student to novice nurse to expert.

In the United States, each state's Board of Nursing delineates who is responsible for the practice of the student nurse. 

Patricia Benner has written the textbook From Novice to Expert.. 

You might try these organizations in terms of any formal guidelines that exist.

No, I have not seen any formal guidelines, But many authors have written about the informal  Guidelines. Some refer to it as the hidden curriculum. Kath Melia's work on "Nurses' occupational socialization is very Good and our work on " Learning nursing" discussed some of the ways student nurse navigate their war through training.

This article may be of interest:“This is nursing”: Nursing roles as mediated by precepting nurses during clinical practice- by Elisabeth Carlson, Ewa Pilhammar, Christine Wann-Hansson.

Regards Carmen