SHAMED ex-minister Louise Haigh was moved from an earlier frontbench role after growing close to a nationalist politician.
The ex-Transport Secretary, who quit last month over a fraud conviction, struck up a friendship with Colum Eastwood when she was Shadow Northern Ireland Secretary from 2020-21.
At the time, Mr Eastwood, 41, led the Social Democratic and Labour Party which backs a united Ireland.
The politics of Northern Ireland are sensitive given the history of sectarian violence during The Troubles.
And Labour insiders were worried by the friendship’s potential impact, The Sun on Sunday has been told.
Sir Keir Starmer moved Ms Haigh, 37, to Shadow Transport Secretary in his 2021 reshuffle.
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The source said: “Northern Ireland is a sensitive brief.
“You have got to tread the path between the nationalists and the Democratic Unionist Party.”
Ms Haigh and Mr Eastwood did not respond to requests to comment, while Labour declined to comment.
Ms Haigh quit as Transport Secretary nine days ago after it emerged she had committed a fraud offence in 2014.
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The year before she had told police that she had lost her work phone in a mugging, and later found it had not been taken but failed to inform officers.
She was given a conditional discharge following the incident which happened before she became MP for Sheffield Heeley.
Haigh described the incident as a genuine mistake from which she did not make any gain.
She said Sir Keir knew of her conviction.
He has said she was only asked to resign after “further information came to light” but has declined to say what.