Agency workers across the UK were set to receive a pay and conditions boost when new rights come into force today.
The Agency Workers Directive was introduced on 1 October, giving equality with directly employed staff after 12 weeks in a job.
Union leaders said that agency workers will receive a pay rise running into thousands of pounds and new rights to holidays, sick pay, maternity and paternity leave and access to staff perks such as health benefits.
Billy Hayes, general secretary of the Communication Workers Union, said: "What we've achieved is the delivery of the best possible Christmas present for the majority of our agency members - won in the teeth of fierce resistance from vested interests who have demonstrated that the spirit of Scrooge is alive and well in the 21st century.
"Six years after the launch of the CWU's campaign in 2006, hundreds of thousands of agency workers across the UK can now finally look forward to some basic employment fairness.
"Not so very much to ask for, you would have thought, yet it's been a fight that has pitched the trade union movement against successive UK governments and commercial interests - some of which are even now trying to circumvent this welcome piece of European legislation."