Women workers will have the most to gain or lose, whoever wins Thursday's General Election, according to the TUC.
The union body has analysed the main party manifestos and concluded that an unintended consequence of a Conservative victory could well be an extension of the compensation and claims industry.
Ironically, the Tories have consistently criticised burgeoning levels of compensation payouts as a "compensation culture".
Key Labour proposals to extend rights at work would mainly benefit women, said the TUC.
Stopping employers including bank holidays in the four weeks minimum paid holiday provided by European rules would benefit 1.4 million full-time workers and 1.5 million part-time, a total of 2.9 million altogether.
The majority of these workers would be women, according to research by the Low Pay Commission included in the TUC's analysis.
Women would be the main beneficiaries of Labour's proposed increases in the minimum wage – in excess of the average rise in earnings.
The planned 4.1 per cent increase in 2005 would benefit 1.2 million workers and 1.3 million would gain from the 5.9 per cent increase in 2006 – again a big majority would be women.
The Low Pay Commission estimated that two thirds of gainers from the last rise were women and half of all gainers were part-time women workers.
Increases in maternity leave and Labour's promises to extend child care would also benefit women at work.
By contrast, Conservative plans would reduce rights at work, and the main losers would be women, suggested the TUC.
The key Conservative proposal was to opt out of the EU Social Chapter.
But a raft of measures that either mainly affected women, or had been mainly used by them, had come through the social chapter, including seven million part-time workers gaining protection against discrimination and four million parents gaining the right to take unpaid parental leave.
Other benefits from the legislations including giving everyone with a caring responsibility the right to take unpaid emergency leave, simplifying the burden of proof in equality cases and making it easier to prove discrimination.
Other Social Chapter measures included rights to information and consultation recently introduced, and protection for employees who have been employed on successive short term contracts.
A surprising conclusion from the TUC study was that the Conservative proposal to introduce costs into employment tribunals would deter employees from taking cases in the short term.
But in the longer term it would encourage "claims farms" to extend their operations to employment tribunals, thus inadvertently increasing the "compensation culture" in employment relations.
At present most cases in employment tribunals do not involve the award of costs – a regime designed to keep cases informal and deter employers and applicants from using expensive legal representation, said the TUC.
The awards of costs would for the first time make encouraging wronged employees to take cases an attractive business model, it added.
TUC general secretary Brendan Barber said: "No one will be very surprised that Labour offers a better deal for people at work, while the Conservatives will reduce rights. But it is striking that the battleground issues will overwhelmingly affect women at work - particularly the low paid.
"Many say there is little or no difference between the parties, but this analysis shows that millions of low paid women workers stand to gain or lose from the outcome of this election.
"Conservative plans to award costs in routine tribunal cases are clearly designed to deter employees from bring cases, but they may have exactly the opposite effect when the day-time TV adverts from the claims industry start."