I have been with my boyfriend now for 4 months and at first my daughter adored him, she would run to him each time he arrived at our house and she would play. I recently went on holiday (without my boyfriend)and since we returned she does nothing but cry continuosly and loudly when he enters the house, and had began to cling to me contiuously. He tries really hard with her and has not give up, we have tried days out but she screams if she knows he is pushing the pram, or tries to hold her hand to walk or picks her up. We have tried to ignore it and she just follows me around like a lost sheep, I have attempted to comfort her but then she just clings to me the whole time. I don't know what to do for the best. I NEED SOME TIPS OR ADVISE PLEASE we are trying our best to make everyone happy (my 4 year old daughter bonds well with him)

She is simply not used to him yet.
And its possible that he is not used to her. Babies can easily pick up on adults anxieties. And if he is in anyway anxious or stressed about caring for her, or being around her, she will feel it.

Both situations are normal. Give it more time, and don't push her.

It might be a developmental thing, especially since she went to him before your trip. Around 15-18 months of age, children can go into a "mommy" phase where only mommy is good enough. No one else will do. Could something like this possibly be the explanation? Does she act this way with anyone else?

Thanks people, she doesn't act like this towards anyone else, as I say, for about a month she would run to him at the door to greet him and be picked up and now she just throws kind of a paddy

I bet she can feel that he is taking away from your time with her :P babies are smarter than we think. Even if they can't say or communicate it.

Or she could be like my niece, and its something as simple as his eyebrows :P my niece flipped out at my uncle! He has very Italian large eyebrows. And it freaked her out.