SDLP leader Colum Eastwood at the SDLP election manifesto launch. Picture by Hugh Russell

People who vote for nationalist and republican parties in Northern Ireland do not necessarily support a united Ireland, the Secretary of State has said.

Launching the Conservatives' Northern Ireland manifesto, James Brokenshire said the conditions for calling a border poll on unification were "not remotely satisfied".

The constitutional question has gained greater public prominence since the UK voted to leave the EU - a referendum that saw 56 per cent of the electorate in Northern Ireland vote to remain.

Under the terms of the 1998 Good Friday Agreement, the incumbent secretary of state is obliged to call a border poll if there is evidence of a shift in public opinion towards Irish unity.

In March's snap Assembly poll, Stormont lost its long-standing unionist majority for the first time. At Westminster, there are 11 outgoing unionist MPs and seven nationalist and republicans.

At the manifesto launch in Belfast, Mr Brokenshire was asked whether a similar reversal of the pro-unionist majority of MPs in the general election would influence the test on a border poll.

"I remain satisfied on the basis of all reliable indicators of the continued support for the devolved administration, the principles and the structures and institutions that are underpinned within the Belfast Agreement (1998) and its successors, and I am very clear that the requirements for a border poll are not remotely satisfied," he said.

"Obviously we keep these issues under very close and careful review but I think in terms of the way people vote, that people may vote for one party but that doesn't necessarily mean they want to see a change to the institutions, that they want to see a change to the foundations that underpin all of that stability that has been achieved from the Belfast Agreement and thereafter."

At the same time the Tories were launching their manifesto for the north, across the city the SDLP called for a post-Brexit border poll at their own manifesto launch.

SDLP assembly member Claire Hanna's infant daughter. Picture by Hugh Russell

Mr Brokenshire said legislation required the incoming government to keep the situation under review.

"As I see it, the support for those institutions, the support for Northern Ireland remaining a core part of the United Kingdom, remains very firmly there," he said.

The Conservative manifesto document rules out any possibility of the region being administered on the basis of joint authority between the UK and Irish Republic if a new powersharing executive is not formed following the resumption of negotiations after the General Election.