The party leaders will be meeting with Labour Leader Jeremy Corbyn, the Liberal Democrats, SNP and Plaid Cymru.
The meeting of representatives from the various political parties comes as pressure mounts on Conservative Party leader Theresa May from various sides over a potential Brexit deal with the European Union.
DUP Leader Arlene Foster has reiterated her party’s stance that they will not back a deal which results in a trading border down the Irish Sea, which would mean Northern Ireland being more closely aligned in terms of rules and regulations with the Republic of Ireland the EU than the rest of the UK.
Speaking ahead of Monday’s meeting, Michelle O’Neill said: “This is the latest in a series of engagements and initiatives which the parties have taken together to demonstrate that the DUP and British government do not represent the cross-community majority of people in the North who voted against Brexit. This will be followed by a meeting with An Taoiseach Leo Varadkar on Wednesday.
“The Brexit negotiations are now in a crucial phase and this is another crucial show of unity when we will once again be asserting our common position that the ‘backstop’ as already agreed must be maintained.
“The backstop is the absolute bottom line for Sinn Féin, SDLP, Alliance and Green Party as we enter the endgame of the Brexit negotiation process on Britain’s Withdrawal Agreement with the EU27.”
The DUP leader meanwhile over recent days said “no unionist” could back Theresa May’s apparent advocacy of a withdrawal treaty that includes a Northern Ireland specific backstop measure to avoid a hard border on the island of Ireland.
In a letter to the DUP, which was leaked to the media, Mrs May insisted such a backstop would never come into force.
Mrs Foster said her party was fundamentally opposed to any divorce deal that saw Northern Ireland operate under a different regulatory arrangement to the rest of the UK.