POLITICAL chaos in Northern Ireland will not derail Brexit, Secretary of State James Brokenshire has said.

With a Stormont election on the cards, Mr Brokenshire warned the parties of the dangers of running divisive campaigns and how they could hamper efforts to rebuild power sharing in Belfast.

A deadline of 5pm on Monday has been set for Sinn Fein to nominate a deputy first minister to replace Martin McGuinness.

His resignation was precipitated by the Renewable Heat Incentive (RHI) scandal - a botched eco-scheme set to cost £490 million - but the row also reignited a range of other disputes dividing the DUP/Sinn Fein-led coalition.

Mr Brokenshire said Brexit would not be hampered by a potential 25-day Stormont election campaign, polling in late February or early March and a possible three weeks of negotiations following that to form a new executive.

"I should also stress that we are not delaying the (Brexit) timetable. We still remain absolutely committed to triggering the Article 50 process by the end of March," the Secretary of State told the BBC's Andrew Marr Show.

"Nothing changes that."

Mr Brokenshire said a Stormont election was increasingly likely but that contacts with the parties are ongoing.

He also said Northern Ireland should not lose out in the Brexit negotiations if there is no serving first and deputy first minister at Stormont.

He said the ministers would remain in their roles even with an election and they will continue to be consulted.

Mr McGuinness's resignation automatically removed DUP leader Arlene Foster from her position as first minister - as executive structures dictate one cannot govern without the other.

Mr Brokenshire refused to be drawn on the possibility of Northern Ireland being run on the basis of a "joint authority" with Dublin.

"I'm not contemplating alternatives to devolved government in Northern Ireland," he said.

The political crisis in Stormont will come to a head on Monday afternoon as the Assembly sits.

The reappointment process is one issue to be raised, along with emergency proposals by DUP Economy minister Simon Hamilton aimed at reducing the RHI overspend and a Sinn Fein motion of no confidence in DUP Speaker Robin Newton.

Mr Newton has been under political pressure over his handling of a recalled Assembly session to debate RHI before Christmas.

He has also been forced to defend himself against conflict of interest accusations in regard to his handling of Assembly exchanges on a controversial charity in his east Belfast constituency.

The devolution meltdown has cast a shadow of uncertainty over a series of big ticket Stormont Executive plans.

One of those is a payment scheme for households losing out under the UK Government's so-called "bedroom tax" and, also on Monday, DUP Communities minister Paul Givan will by-pass the Executive to ask for direct Assembly approval for the support measure.