Supreme Court justices have rejected a landmark appeal by Pimlico Plumbers over the employment status of a plumber, in a case likely to have a major impact on the so-called gig economy.

Five judges at the UK’s highest court unanimously upheld earlier decisions that Gary Smith, a plumber who worked for Pimlico Plumbers for nearly six years, could claim “worker” status, even though he was described in his contract as a “self-employed operative”.

The court ruled in London on Wednesday that an employment tribunal was “entitled to conclude” that Smith was a worker.

As a worker Smith would be entitled to employment rights, such as holiday and sick pay.

The Supreme Court ruling means that an employment tribunal can now proceed to examine his action against Pimlico Plumbers as a worker, including a claim that he was unfairly dismissed.

The Equality and Human Rights Commission, which has funded Smith’s case since 2015, said thousands of workers in the gig economy are set to benefit from the ruling.

The commission’s chief executive Rebecca Hilsenrath, said: “If you wear the uniform, if you drive the branded vehicle, if you only work for one business, you are employed.

“That means you are entitled to the appropriate protections and adjustments which go with the job, to enable you to work safely and productively.”

TUC general secretary Frances O’Grady said: “This case has exposed how widely sham self-employment has spread. Bad employers are using every trick in the book to deny staff basic rights.

“It’s time to end the Wild West in the gig economy. The government must get tough on rogue bosses and give unions the right to organise in more workplaces.

“People shouldn’t have to go to court to get a fair deal at work. Companies that treat their staff like disposable labour must be brought to book.”