The new Prime Minister Liz Truss has said she is determined to restore the "balance" between communities in Northern Ireland.
Ms Truss said relations have been "damaged" by Brexit's Northern Ireland Protocol and she wants to work with all Stormont parties to "fix the issues".
She was responding to SDLP leader Colum Eastwood, who demanded she make clear whether she was "on the side of the DUP or on the side of struggling people in Northern Ireland".
Read more: Analysis: Liz Truss success or failure in Northern Ireland still shaped by Brexit fall-out
The Foyle MP said many people were "starving and freezing in their homes" but tailored support was "much harder to achieve because the DUP are refusing to form a government at Stormont".
He added: "The new Prime Minister has a choice to make: She can either be on the side of the DUP or on the side of struggling people in Northern Ireland. So whose side is she on?"
In her first Prime Minister's Questions, Ms Truss responded: "I want to work with all of the parties in Northern Ireland to get the Executive and the Assembly back up and running so we can collectively deliver for the people of Northern Ireland.
"But in order to do that we do need to fix the issues of the Northern Ireland Protocol, which has damaged the balance between the communities in Northern Ireland.
"I am determined to get on with doing that and I am determined to work with all parties to find that resolution."
Stormont has been in limbo for months after the DUP withdrew from power-sharing in protest over the protocol, which has angered unionists for introducing new checks on goods moving between Great Britain and Northern Ireland.
Former Northern Ireland secretary Shailesh Vara asked Ms Truss to confirm she will press ahead with a Westminster bill to override the protocol if a negotiated resolution with the European Union is not "forthcoming".
The Prime Minister replied: "My preference is for a negotiated solution, but it does have to deliver all of the things we set out in the Northern Ireland Protocol Bill.
"And what we cannot allow is for this situation to drift because my number one priority is protecting the supremacy of the Belfast/Good Friday Agreement."
Earlier in the Commons, the new Secretary of State Chris Heaton-Harris said there is a "fairly obvious landing zone" to resolve the impasse through negotiations.
But Mr Heaton-Harris, who replaced Mr Vara the previous day as Northern Ireland secretary, said the government would also continue progressing the Protocol Bill.
DUP MP Sammy Wilson told Mr Heaton-Harris: "I hope he will be successful in doing what is necessary to get Stormont restored, namely removing the poison of the protocol."
Meanwhile, Stormont Finance Minister Conor Murphy has urged Ms Truss to deliver a package of measures to help businesses in Northern Ireland hit by rising energy prices.
Speaking during a visit to Dungannon, Co Tyrone, the Sinn Féin minister said he had heard first-hand of the hardship businesses were facing.
He said: “Every day we hear of businesses left with no choice but to cease trading or to compress their opening hours in order to make savings on running costs.
“The unpredictable, crippling energy bills facing our small businesses are not sustainable.
“For months I have been calling on the British Government to intervene to support businesses and their workers.
“Liz Truss must act now before it’s too late for more businesses.
“The Westminster Government must step up and urgently deliver support which makes a real difference.”
Mr Murphy said action should be taken to reduce VAT and duties on fuel and energy bills.
He added: “The reduced VAT for the hospitality sector must also be reinstated to assist these businesses, which were so adversely impacted by the pandemic.
“Given the ever-deepening crisis, more will need to be done to tackle the scale of energy bills expected over the winter months.
“It is essential that any package of measures put in place is delivered quickly to support our businesses and protect the jobs of those they employ.”
It comes as another energy company announced it was increasing prices in Northern Ireland.
Click Energy, the smallest of five electricity suppliers in the region, said it was increasing prices by 28.2% at the start of October, affecting 26,000 customers.
Earlier this week, gas supplier Firmus Energy announced a 56.3% price rise for Northern Ireland customers.
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