The UK postal workers’ union has issued a strike warning to Czech billionaire Daniel K?etínsky if he fails to meet their demands in his Royal Mail takeover bid, raising the threat of industrial action that has dogged the company in the past.

Dave Ward, general secretary of the Communication Workers Union, said the group had decided to “take whatever steps necessary to protect” employment conditions and Royal Mail’s universal service obligation to deliver letters and parcels across the country for the same price.

“There are certain things that if they are attacked, we would take industrial action. We would call a ballot of our members,” he told the Financial Times, adding the union would also challenge a separation of the group’s struggling letters’ business and its more profitable parcels operation.