4yr old dd will only poo in nappies

[mystified76]

My dd1 is 4 in january, she has been dry in the day for a year, but still refuses to do a poo on the toilet.
She doesn't have any accidents at all in her pants, she can hold onto a poo for up to a week (i think 8 days is her record) and will then ask for a nappy and do an absolute huge poo. She totally refuses to go on the toilet for a poo but is fine for wees.
We have tried every bribe you can think of...chocolate, sticker charts etc etc... the latest bribe is a trip to euro disney but even that isn't working! Any ideas? i have said to dh,mil etc for ages that it will resolve itself in time but keep getting comments and now even my mum who is usually sooo supportive has made remarks
What should i do next?

My son just turned 4. He had no problems peeing in a toilet, but still only poops in a nappy! I am so glad I came across this forum - makes me feel better, at least I'm not on my own lol
That's not it - my son refuses to pee anywhere but home, and will always take his trousers off when he needs to pee (and pants and socks).
Anyone came across that?

Have just found this thread. Having this problem with a nearly 5 year old. How did everyone get on eventually? Need a light at the end of the tunnel...thank you.