Cherie Blair has won the crucial support of the European Commission in her battle with her husband, Tony, over his refusal to grant parental leave to more than three million fathers and mothers.
With around two weeks to go until the birth of her fourth child, Mrs Blair was last night celebrating a European ruling which puts the Prime Minister under huge pressure to change the rules.
Mrs Blair has become a prominent figure in the campaign, fronted by the Trades Union Congress, for more generous maternity and paternity leave. She has already advised the unions that the British regulations have not been properly implemented in the UK.
The current legislation, which came into force last December, allows mothers and fathers 13 weeks' unpaid leave after a child's birth or adoption, at any stage until the child's fifth birthday.
But it does not include more than three million parents whose children were born before 15 December 1999 - a restriction that puts Britain at odds with many of its EU neighbours.
However, in a decision announced last week, the European Commission has ruled that a similar exclusion clause introduced by the Irish government is illegal and must be changed.
The Government is already facing a High Court challenge from the TUC on 16 May over its refusal to back-date leave - led by Mrs Blair, a prominent employment QC. Negotiations are currently taking place between the TUC and the Department of Trade and Industry to reach an agreement before the court date.
Last night, the TUC said the Government would face humiliation if it refused to back down and went ahead with the High Court case.
"We hope that, even at this late stage, the news from Ireland will be enough to persuade the Government to think again," added a spokeswoman. "There is still time for them to back down and give all working parents with children under the age of five the right to parental leave."
This view was shared by the Maternity Alliance which said it was "delighted" at the decision.
"We were astounded when the Government did not bring in the legislation for all children under five," a spokeswoman commented. "It was sheer mean-spiritedness and many parents were in shock. We are delighted that the commission has made this decision and we feel sure that it will mean the Government will now have to back down."
The TUC is also backed by the Equal Opportunities Commission. Julie Mellor, the EOC chairwoman, has already urged Mr Blair to extend the leave to include all working parents with children up to the age of five.
The Department of Trade and Industry defended the cut-off date by saying that it had been imposed to ensure that demand for parental leave built up slowly so that the "goodwill of employers is maximised".
Next week, Stephen Byers, the Trade and Industry Secretary, will announce a review of parental rights.
This will look at increasing maternity pay, maternity leave and the possibility of paid parental leave.
But campaigners say the Government needs to change the legislation introduced last December.
The Prime Minister is also coming under increasing pressure to make state payments of up to £150 a week for parental leave as part of the Labour manifesto for the next general election.
Critics claim that the system of unpaid leave makes it impossible for thousands to take advantage of it. Research by Ruth Kelly, a Labour MP, suggested that the Government could afford to introduce a payment.
Mr Blair has admitted that he does not plan to totally stop working after his new baby is born. But he does plan to take limited paternity leave.
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