Warsaw's central business district is booming alongside Poland's economy, but those teaching yoga and taking coffee orders in bustling premises under glass and steel office towers are often Ukrainian.

Economists and entrepreneurs agree: Refugees from the Russian invasion of Ukraine have proven a huge boost to Poland's economy -- but now their contribution may be at risk.

A law governing Ukrainians' protected status expires at the end of the month and President Karol Nawrocki has yet to sign off on a bill to renew it, threatening a million people with legal limbo.

At the ElFlex yoga and fitness centre, the young women stretching and balancing in complicated poses under the coloured lights maintain their poise, but concern is rippling through the community.

Gym owner Lisa Kolesnikova, 28, grew up in the Ukrainian city Zaporizhzhia, but she built her business in Poland.

She now owns two yoga studios and has franchised two more. Two years ago most of the customers and all of her staff were from Ukraine or Belarus. Now, that's changing.

"Polish clients come to us, and the girls now conduct training in Polish. They like us and, in fact, I have never........

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