Ministers warn of a crisis after John Bercow says MPs cannot vote again on motion they rejected last week.
The girl and two boys died after an incident outside a hotel hosting a St Patrick's Day event in Tyrone.
Property tycoon Fergus Wilson is calling it a day after years of controversy over his rental policies.
Jane Kennedy says she made the decision after Luciana Berger left the party.
The UK also faces a "growing threat" from the far right, security minister Ben Wallace says.