diff --git a/app/main/forms.py b/app/main/forms.py
index c543dc2a2..b2fc0573e 100644
--- a/app/main/forms.py
+++ b/app/main/forms.py
@@ -62,6 +62,7 @@ from app.models.roles_and_permissions import (
     roles,
 )
 from app.utils import merge_jsonlike
+from app.utils.user import distinct_email_addresses
 
 
 def get_time_value_and_label(future_time):
@@ -1060,6 +1061,10 @@ class InviteUserForm(BaseInviteUserForm, PermissionsForm):
 class BroadcastInviteUserForm(BaseInviteUserForm, BroadcastPermissionsForm):
     email_address = email_address(gov_user=True)
 
+    def validate_email_address(self, field):
+        if not distinct_email_addresses(field.data, self.invalid_email_address):
+            raise ValidationError("You cannot send an invitation to yourself")
+
 
 class InviteOrgUserForm(StripWhitespaceForm):
     email_address = email_address(gov_user=False)
diff --git a/app/utils/user.py b/app/utils/user.py
index 577abb305..23a12ccb1 100644
--- a/app/utils/user.py
+++ b/app/utils/user.py
@@ -66,3 +66,14 @@ def _email_address_ends_with(email_address, known_domains):
         ))
         for known in known_domains
     )
+
+
+def normalise_email_address_aliases(email_address):
+    local_part, domain = email_address.split('@')
+    local_part = local_part.split('+')[0].replace('.', '')
+
+    return f'{local_part}@{domain}'.lower()
+
+
+def distinct_email_addresses(*args):
+    return len(args) == len(set(map(normalise_email_address_aliases, args)))
diff --git a/tests/app/main/views/test_manage_users.py b/tests/app/main/views/test_manage_users.py
index 11a74420c..3d69afe6e 100644
--- a/tests/app/main/views/test_manage_users.py
+++ b/tests/app/main/views/test_manage_users.py
@@ -1443,6 +1443,70 @@ def test_user_cant_invite_themselves(
     assert not mock_create_invite.called
 
 
+@pytest.mark.parametrize('email_address', (
+    'test@user.gov.uk',
+    'TEST@user.gov.uk',
+    'test@USER.gov.uk',
+    'test+test@user.gov.uk',
+    'te.st@user.gov.uk',
+    pytest.param('test2@user.gov.uk', marks=pytest.mark.xfail),
+    pytest.param('test@other.gov.uk', marks=pytest.mark.xfail),
+))
+def test_broadcast_user_cant_invite_themselves_or_their_aliases(
+    client_request,
+    service_one,
+    mocker,
+    active_user_with_permissions,
+    mock_create_invite,
+    mock_get_template_folders,
+    email_address,
+):
+    service_one['permissions'] += ['broadcast']
+    page = client_request.post(
+        'main.invite_user',
+        service_id=SERVICE_ONE_ID,
+        _data={
+            'email_address': email_address,
+            'permissions_field': []
+        },
+        _expected_status=200,
+    )
+    assert normalize_spaces(page.select_one('span.govuk-error-message').text) == (
+        "Error: You cannot send an invitation to yourself"
+    )
+    assert mock_create_invite.called is False
+
+
+@pytest.mark.parametrize('extra_service_permissions', (
+    pytest.param([], marks=pytest.mark.xfail),
+    ['broadcast'],
+))
+def test_platform_admin_cant_invite_themselves_to_broadcast_services(
+    client_request,
+    service_one,
+    mocker,
+    platform_admin_user,
+    mock_create_invite,
+    mock_get_template_folders,
+    extra_service_permissions,
+):
+    service_one['permissions'] += extra_service_permissions
+    client_request.login(platform_admin_user)
+    page = client_request.post(
+        'main.invite_user',
+        service_id=SERVICE_ONE_ID,
+        _data={
+            'email_address': platform_admin_user['email_address'],
+            'permissions_field': []
+        },
+        _expected_status=200,
+    )
+    assert normalize_spaces(page.select_one('span.govuk-error-message').text) == (
+        "Error: You cannot send an invitation to yourself"
+    )
+    assert mock_create_invite.called is False
+
+
 def test_no_permission_manage_users_page(
     client_request,
     service_one,