My partner and I separated before I realised I was pregnant. We both wanted to keep the baby but decided not to rekindle the relationship. He agreed to stay with me for three months after she was born to help look after her. However, he left two weeks after the birth, complaining about, among other things, lack of sleep. Since then, his visits have declined and he only sees our daughter once a week for three or four hours. He has a new girlfriend and now wants our daughter to stay with them overnight.

Our daughter is only nine weeks old and I am finding it very difficult to let her go. He has told me to get over it and is threatening to reduce financial support unless I agree. We are going to mediation but I don’t know how to express how I feel and present my case. C, via email

Congratulations on the birth of your daughter. The organisations listed in my reply both run great helplines if you needed to chat this through with someone further, and two of them can give you legal advice if necessary. I consulted all three before replying to you.

You also told me your daughter’s father was named on the birth certificate, which means you both have parental responsibility for her.

However, it’s important to note that no one has an automatic right to contact. Family law is rightly concerned with what’s best for the child – set out in the Children Act 1989, specifically Section 1: the Welfare of the Child.

You need to think about what you believe is best for your daughter and present that at mediation (great that you are trying mediation). I suggest calling the helplines, reading the act mentioned above, reading the paper below and then presenting it calmly as “this is what I think is best for our daughter at the moment” and explaining why.

It’s great that your partner wants to be involved. But as your daughter and her father have not really had much chance to bond (despite your best intentions) and she is so little, I think they need to build up this bond with frequent daytime visits until you feel comfortable with her going to stay overnight. Especially given how hard he has already found the sleepless nights. There’s plenty of time for overnight stays in the future, when they are more used to each other.

You asked if I knew of any recent studies that talked about a baby’s emotional attachments in situations such as these. Dehra Mitchell, a psychotherapist and chair of fpct.org, pointed me in the direction of a paper called “Special considerations for infants and toddlers in separation/divorce” by Jennifer E McIntosh (June 2011). I will send you a copy, but you can also find it on the web.

Parental responsibility means that both of you should consult, and consent, on matters such as schooling, medical treatment, etc. If you can’t agree on these issues or contact arrangements then the partner who doesn’t agree can take it to family court, which would make a legally binding decision. I urge you to try to sort things out without resorting to court and I know you want that too.

Gingerbread said: “The welfare and best interests of a child are the most important considerations when coming to a contact agreement. Your daughter is very young and this has to play an important part in negotiations with your ex-partner. If you are breastfeeding, this could support your argument for your daughter to stay with you at the moment and for visits to be conducted at your home. As your ex-partner’s contact with your daughter has declined to a few hours a week, we would recommend, instead of jumping to overnight stays, that you both work on an agreement that sees contact gradually building up.”

A non-resident parent who does not pay maintenance is still entitled to see their child. You can’t refuse contact because they don’t pay sufficient, or any, maintenance. Child maintenance and access rights are treated as separate legal issues by the court. Your ex is legally bound to pay the statutory entitlement until your daughter is at least 16. If, however, your daughter ends up staying with her father for more than 52 nights of the year, this will reduce the amount of child maintenance he has to pay.

• childrenslegalcentre.com, tel: 08088 020008; gingerbread.org.uk, tel: 0808 802 0925; rightsofwomen.org.uk, tel: 020 7251 6577.

First published in The Guardian Family section on 8th February 2013.