SDLP leader Dr Alasdair McDonnell has warned that other parties must think carefully about who they back as a government is established.
The former GP fought off a stiff DUP challenge to retain his South Belfast seat by less than a thousand votes.
He said the next Parliament would have a significant impact on everyone in Northern Ireland.
“The SDLP remains committed to opposing the Tory agenda and ensuring that we get the best possible deal for Northern Ireland.
“Other parties must now think carefully about who they will back in the coming days as a government is established.”
The SDLP is a sister party of the Labour Party but Mr McDonnell has said it would make its own mind up and has called for a “prosperity process” to support the peace process.
The DUP and UUP were unable to agree a pact for the constituency and Dr McDonnell held on by a majority of 906 votes.
DUP Stormont junior minister Jonathan Bell said he had come within a whisker of making South Belfast a unionist stronghold.
“That is something that unionism needs to learn very much from.”
Sinn Fein’s Mairtin O Muilleoir, a newcomer to the constituency, took 5,402 votes.
Ukip’s Bob Stoker, a former Ulster Unionist, won 1,900 votes.