If you are removing a load bearing wall, you will need to install a beam to support the structure above, quite often this support will be either a steel beam or a reinforced concrete lintel or a steel lintel, for larger openings you will usually need to use a steel beam.
Walls are load bearing if they are supporting floors, walls, roofs or other structural elements. If the wall you are removing is load bearing you will need to comply with the Building Regulations, for further advice you can speak to your councils local building control department or you can also try contacting private sector Approved Building Control Inspectors if you prefer.
If you need a beam calculation report, please take a look here.