Labour supporters in the North of Ireland are being wooed by their left-leaning allies in the Republic after being snubbed by colleagues in London.
A legal challenge led by GMB shop steward Andy McGivern last year forced the British Labour Party to extend membership rights to Northern Ireland residents after 80 years of an increasingly controversial membership ban.
Labour's ruling national executive committee reluctantly conceded the case because it believed that the courts would find it guilty of discrimination.
And last year's party conference accepted lifting the ban by 86% of the vote.
However, the party gave itself powers to decide if members in any part of the UK would then be allowed to set up constituency parties.
The national executive recently agreed that members in England, Wales and Scotland would have this right but not those in the North.
Mr McGivern has written to Prime Minister Tony Blair saying that "Northern Ireland members are not being made welcome and cannot participate in any aspect of party life."
He is requesting an urgent meeting with Mr Blair and may revive his legal challenge.
He said: "This decision is deeply disappointing and means that Labour members in Northern Ireland cannot participate in policy-making and send delegates to Labour's annual conference or other policy forums."
The attitude of the party in London appears to be in stark contrast to what Mr McGivern calls "the much more positive attitude" of the Irish Labour Party in Dublin.
Party Chair Liz McManus TD has invited Mr McGivern to a meeting in the Dail next week to meet party leader Pat Rabbitte and his parliamentary team.
Mr McGivern said: "We want to work fully with the Irish Labour Party, which is the third party in politics south of the border, and help build a labour movement that works together, north and south of the border."
He added: "The Irish Labour Party recognised the fact that socialists in Northern Ireland had no political voice and in December 2002, without any pressure at all, decided to admit members in Northern Ireland. The Irish Labour Party wants to set up a forum in Northern Ireland allowing all shades of socialism to participate and be able to air their views."
