The Government was today urged to close legal loopholes that could be denying up to nine million workers their employment rights.
The TUC said workers across the UK were missing out on protection against unfair dismissal and rights to family-friendly measures because they did not legally qualify as employees.
Casual staff, agency workers, freelancers and home workers were among those only considered to have worker status rather than the more formal employee status.
Seafarers, some civil servants and members of the clergy also had fewer employment rights than other workers, said the TUC.
Low-paid, low-skilled workers - mainly women or from ethnic minority groups - were often worst affected by the lack of employment rights, the Government was told.
TUC general secretary-elect Brendan Barber said: "Employers are more likely to use casual workers than ever before. There is a huge gulf between the rights enjoyed by employees and those that workers are entitled to.
"The result is the creation of a two-tier workforce - with employees enjoying job security and employment rights, and casual, agency and freelance workers experiencing job insecurity and worsening job conditions.
"If the UK is to stay a fair place to work, the Government must close the loophole quickly."
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