In a statement released on Friday, the union Unite said the strike will continue from Monday to 13 February.
"The NHS workers taking strike action have their union's unwavering support. They face the same risks as NHS-employed staff. Why on earth are they being paid significantly worse while being treated disgracefully? It's time to end this injustice. It's time to bring these workers, employed by Serco not the NHS, back into NHS employment", Unite General Secretary Sharon Graham said.
"Hundreds" of cleaners, porters, security personnel, catering and reception staff are expected to join the strike across three London hospitals - St. Barts, Royal London Hospital, and Whipps Cross - according to the statement.