Only six of 40 public appointments made by the Ministry of Defence this year have gone to women despite a Government push to fill at least half of vacancies with women, official figures show.
Although the overall proportion across Whitehall is rising - hitting 44% in the first half of this year - many departments are falling well short and several have gone backwards.
Labour said this month's figures showed the Government was set to miss its 50% aim - with 10 departments performing worse last year than in the previous 12 months.
Taking out the two best performers showed the proportion across the rest remained at just 30%, it said, painting the failure as part of a wider issue reflected in a lack of women in the cabinet.
Between April and September the Ministry of Justice appointed women to 102 of 185 vacancies, with only the Cabinet Office (three of four) and Communities and Local Government (two of four) also reaching 50%.
The Department for Culture, Media and Sport came close with 48% - but the MoD was one of six to prefer female candidates in fewer than a third of cases.
None of the three made by the Department for Education or the two by the Department for Transport went to women.
Appointments to the boards of public bodies are regulated by the Commissioner for Public Appointments which monitors equality issues.
In 2012/13 - the first year the statistics were published - 37.15% of appointments were of female candidates and 39.2% in 2013/14.
The only departments which hit 50% in 2013/14 were the Foreign Office - two of four - and the Home Office, 36 of 68.
Shadow equalities minister Gloria de Piero said: "David Cameron and Nick Clegg claim they want more women at the top of society but their Government's actions tell a different story.
"They are failing on their commitment to gender equality in Government appointments and preside over a cabinet that's two-thirds male.
"A Labour Government in contrast will lead by example. Ed Miliband has said he wants 50% of his cabinet to be women, and we will govern in the interests of women, from introducing 25 hours free childcare for three and four-year-olds of working parents, or pay transparency to tackle the gender pay gap."
But a Cabinet Office spokesman insisted it was "on track" to achieve 50%.
"As part of this Government's long-term economic plan, we want the very best people on the boards of our public bodies.
"So we have overhauled the appointments process to emphasise skills over experience and to encourage more women to apply for these important positions.
"Before the last general election, only around a third of new appointments went to women.
"We are making strong progress with around 40% going to women last year, putting us on track to meet our aspiration of half of such appointments going to women."