MADRID - Spain's tourism sector is enjoying record growth, accounts for one-tenth of the economy and drives job creation, but a category of hotel workers feel the boom has left them behind.

Cleaners, whose plight has become emblematic of the inequalities enduring in Spain even after the economy rebounded from a deep recession, will now be the first to benefit from changes to labour laws by the two month-old government of Socialist leader Pedro Sanchez.

For Maria del Mar Jimenez, one of the women known as "Kellys", from the Spanish "las que limpian" ("the women who clean"), change cannot come fast enough.

"I live it first-hand. We are 21st century slaves," said the 56 year-old who cleans in a five-star Madrid hotel, describing the constant muscle pain she feels after three decades of work.

As Spain flourished to become the world's second most visited country, and income per hotel room jumped 9.5 percent last year, Jimenez says she and her colleagues ended up having to clean more than 24 rooms a day.

"When the 35 year-olds are my age, what state will their backs be in? They will have arthritis and breathing problems that ruin their lives," she said.

As many Spaniards prepared to pack for their summer holidays, the government pledged on Friday to invest 30 million euros ($35 million) to hire 833 new labour inspectors to uncover abuses of contracts and failures to pay employees.

Prime Minister Sanchez says he is righting the perceived wrongs in labour reforms introduced by his vanquished conservative predecessor Mariano Rajoy, as part of a broad social agenda aimed at appealing to disillusioned left-wing voters.

Austerity-minded Rajoy was criticised by unions for weakening workers' rights with the 2012 labour law, adopted during the darkest period of an economic crisis that left deep scars on the euro zone's fourth-largest economy.

"Our aim is to reinstate workers' rights that were lost during the crisis," Labour Minister Magdalena Valerio told a news conference. "The government is going to push for dignified and decent employment."

But Sanchez's administration has not said it plans to repeal the 2012 law, and, even with the planned changes, hoteliers will still be able to outsource the hiring of cleaners, a factor which unions say contributes to their precarious position.

Jimenez said it was too soon to celebrate.

"We are hopeful, because the minister said she was going to do something, and hope is all we Kellys have left."