Washing Machine Outflow Pipe Overflowing

[tatty]

Hi,

Just bought a new washing machine and plumbed it in. First wash the standpipe(?) where the machine outflow hose is inserted started overflowing during the drain.

I put a drain unblocker wire down there to see if I could clear any blockage but without success.

Our old machines never had this problem so i'm a bit stumped as to the cause.

Blockage in the trap?
Capacity of the pipe?
Power of the pump?

Any ideas welcome.