|The DUP is currently the 4th largest party, with 8 MPs.|
The DUP has threatened to launch a legal challenge against the BBC, weeks after they were excluded from the 2015 general election debates.
Peter Robinson, the DUP leader, accused the BBC of "Treating Northern Irish people like 2nd class citizens" by excluding all NI parties from the debates but including Plaid Cymru and the SNP.
Robinson yesterday met James Harding, BBC director of news and current affairs, but the talks ended without agreement. An appeal currently lodged against the decision with the BBC is due to be heard next month. If that fails, Robinson has said he will take the BBC to court.
A DUP challenge is highly likely to be successful, according to legal experts. It would then make it extremely unlikely that the debates could go ahead, as talks would have to start all over again, and the April cut-off point is approaching very fast.
The BBC and ITV are currently planning to hold two debates involving the Conservatives, Labour, Liberal Democrats, UKIP, Plaid Cymru, the SNP and the Greens.
The DUP is currently the fourth largest party in the Commons, with eight MPs.
A third debate - hosted by Sky and Channel 4 - would feature a head-to-head between Prime Minister David Cameron and Labour leader Ed Miliband.