The British government has asked the High Court in London to block a strike by border control officers planned for Thursday, on the eve of the Olympics.
Immigration and passport personnel at Heathrow and other airports are among those due to go on strike, which is over job cuts.
The Home Office said it believed there was "procedural errors" in a ballot conducted by the PCS union.
Members of the Public and Commercial Services union are in a dispute over job cuts and pay.
In a ballot earlier this month, 57% of PCS members who took part, voted for industrial action. But the BBC reports ccabinet ministers have said only 12% of the union's total members participated.
The PCS has said 8500 Home Office jobs are at risk as a result of government cuts, including the threat of compulsory redundancies at passport control and immigration offices.
