2007 Vauxhall Astra Car pulling when I accelerate

Wow... it could be a few things. Has the check engine light come on? When this happens, does it seem like the clutch may be slipping or chattering? Was the vehicle ever tuned up?

Thanks for reply,
No there's no warning lights what so ever,
It's never been tuned or anything, and clutch seems done, it's more when I'm in higher gear than low gears, of tgat helps?

A clutch is actually more likely to slip or chatter at higher gears.

It's not the clutch it's something with the engine power it's not when I'm using the clutch it's when I use the accelerator

Based on your description, it could be the clutch slipping when you accelerate and more pressure is on it. If you feel it is the engine, then it sounds like a misfire or a fuel related issue.. However, that should have set the check engine light. Have you checked fuel pump pressure to see if it is within the manufacturer's specs?