CAML query not working

I want to filter list items on the basis of sharepoint user group name.

only list items which having Value in Column-Vendor same as Sharepoint group should able to see that list item.

I am using following CAML query

<Membership Type="CurrentUserGroups"><FieldRef Name="Vendor"/></Membership>

but its not working, I tried following also

<Membership Type=\"CurrentUserGroups\"><FieldRef Name=\"Vendor\"/></Membership>

but still its not filtering but showing all list items for the user.