Where to complain about overflowing sewer?

The past 3 days water leaks out from the sewer in our place. Landlord cannot be contacted. The smell is becoming awful day by day. I have young children and our only way out of the house is through the garage where sewer water flows out from the cover on the ground. I need info on where to complain about this in case we still cannot contact the landlord by tomorrow. Thanks.
If the leak /overflow is with in your boundry wall.. your landlord . If outside/ road please contact complaint office of municipality- 44686525. you have to give your street number and your contact phone number. they will act fast. good luck