This addresses a common, day-to-day concern that separated or divorced parents may have about custody and access arrangements for their children.

You and your Ex have split, and he or she has gone on to form a new romantic relationship with someone else.

The relationship may be an established one, or it may be brand-new. But either way your concern, quite understandably, may relate to items such as:

• the amount of time the children spend in the new partner’s company;

• the extent of his/her caregiving, and discipline imposed;

• the overall influence that the new partner may have on your children;

• differences in values or lifestyle that the new partner may expose your children to;

• the “message” that the new partner’s presence will convey to your children (e.g. possibly that your own role in their lives is about to diminish, or that you are being outright “replaced”).

You may wonder whether you are legally-entitled to voice your say or have any influence on the situation, particularly if you are not a fan of the new partner personally.

Can you refuse to co-operate you’re your Ex’s custody / access entitlement, to avoid having the children spent time with a new partner you don’t like? Can you refuse to allow your children to have overnight visits if the new partner is also staying over at your Ex’s home?

The short answer is (generally): No.

You and your Ex both have the right to form new relationships; unless there is a court order in place that expressly prohibits your Ex from exposing your children to any new romantic partners (which, frankly, is rare) then there may be little that you can do.

Of course this presumes that your Ex has valid custody or access rights and is exercising them in a reasonable and appropriate manner, with no concerns over the child’s health, safety or well-being.

If there is doubt, a court will certainly assess the situation from the vantage point of what is in the children’s best interests.

But – leaving aside any normal human resentment or jealousy of your own – the motives for blocking your children’s access to a new partner are likely not based on any legally-recognised concerns. In other words: You probably just have to live with it.

With that said, the situation might be different if you and your Ex have expressly agreed not to expose the children to a new partner (or to do it only gradually) and that agreement is breached. 

If the other Parent Has Parental Responsibility for the children in legal terms. This means that he has a right to have a say about the children’s upbringing and welfare.

The other Parent is entitled to see the children and it is not really up to you to say how those meetings should be conducted.

By dictating how those meetings are conducted or stipulating that he can only see the children whilst you are present, you are obviously affecting the relationship he can have with the children.

If he does not agree with your demand, you cannot force him to comply.

If you prevent him from having access to the children at all, he will have to go to court and apply for an order which forces you to give him access.

Alternatively, you could go to court and apply for an order that sets conditions on the access your husband has to the children.

To prevent your children meeting your husband’s new partner, you could apply for a Prohibited Steps Order under the Children Act 1989.

But to do that you would have to convince the court that it is in your children’s best interest not to meet your husband’s new partner because she would have an adverse influence on them. 

Going to court is not a decision to be entered into lightly and will almost certainly add to your children’s distress.

Frankly, as long as you cannot set out a realistic case that they are going to harm your child in any way, and your ex-partner has a contact order to see your children, then there is not much you can do.

You can try to speak to your ex-partner about the situation, but they may not understand why you don’t want your children to see their new partner and this could cause more friction between you both.

If you think your child is at risk of harm from your ex-partner’s new partner then you must contact the police straight away and if the police support your account then they would involve social services how would take a view on such contact continuing 

Then you may also be able to get an injunction against your ex’s new partner if this was the case and they would not be able to see your children.

But you will only be able to get an injunction if you have strong evidence to support such an application.