diff --git a/app/controllers/users_controller.rb b/app/controllers/users_controller.rb
index 32a135e36..fb1f2f074 100644
--- a/app/controllers/users_controller.rb
+++ b/app/controllers/users_controller.rb
@@ -121,7 +121,9 @@ private
       @resource.errors.add :role, I18n.t("validations.role.invalid")
     end
 
-    if user_params[:phone].present? && !valid_phone_number?(user_params[:phone])
+    if user_params[:phone].blank?
+      @resource.errors.add :phone, :blank
+    elsif !valid_phone_number?(user_params[:phone])
       @resource.errors.add :phone
     end
   end
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 73cf91d0a..df75770f9 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -156,6 +156,7 @@ en:
               taken: "Enter an email address that hasn’t already been used to sign up"
             phone:
               invalid: "Enter a telephone number in the correct format"
+              blank: "Enter a telephone number"
             role:
               invalid: "Role must be data accessor, data provider or data coordinator"
               blank: "Select role"
diff --git a/spec/requests/users_controller_spec.rb b/spec/requests/users_controller_spec.rb
index 8a491f2ca..ce5bba1db 100644
--- a/spec/requests/users_controller_spec.rb
+++ b/spec/requests/users_controller_spec.rb
@@ -850,6 +850,7 @@ RSpec.describe UsersController, type: :request do
             name: "new user ",
             email: "new_user@example.com",
             role: "data_coordinator",
+            phone: "12345678910",
           },
         }
       end
@@ -1312,6 +1313,7 @@ RSpec.describe UsersController, type: :request do
           expect(page).to have_field("user[name]")
           expect(page).to have_field("user[email]")
           expect(page).to have_field("user[role]")
+          expect(page).to have_field("user[phone]")
         end
 
         it "allows setting the role to `support`" do
@@ -1610,6 +1612,7 @@ RSpec.describe UsersController, type: :request do
             name: "new user",
             email:,
             role: "data_coordinator",
+            phone: "12345612456",
             organisation_id: organisation.id,
           },
         }
@@ -1641,6 +1644,7 @@ RSpec.describe UsersController, type: :request do
               name: "",
               email: "",
               role: "",
+              phone: "",
               organisation_id: nil,
             },
           }
@@ -1656,6 +1660,7 @@ RSpec.describe UsersController, type: :request do
           expect(page).to have_content(I18n.t("activerecord.errors.models.user.attributes.name.blank"))
           expect(page).to have_content(I18n.t("activerecord.errors.models.user.attributes.email.blank"))
           expect(page).to have_content(I18n.t("activerecord.errors.models.user.attributes.organisation_id.blank"))
+          expect(page).to have_content(I18n.t("activerecord.errors.models.user.attributes.phone.blank"))
         end
       end