The party will refuse to nominate Stormont speaker.
Hopes of a new power-sharing deal in Northern Ireland have been dealt a fresh blow.
Just hours before politicians were due to gather in Stormont, the DUP said it'll block the election of a new speaker, preventing the formation of a new Executive.
They're protesting against post-Brexit trade arrangements.
The Finance Minister has warned there will be immense consequences if the British Government reneges on the Northern Ireland protocol.
MLAs have been sworn in this afternoon but the DUP is stopping business proceeding until the Northern Ireland protocol is dealt with.
Finance Minister and Eurogroup President Paschal Donohoe has warned the UK Government not to back out of the deal:
Sky's senior Ireland correspondent David Blevins says there'll be implications if Westminster overrides the Northern Ireland protocol to allow a government to be formed: