Pay strikes by hundreds of officers within the Compliance, Policing, Operations and Security Directorate (CPOS) at Transport for London (TfL) will escalate in February.

The workers, who deal with violence and aggression across the TfL network to keep the passengers and staff safe, are paid thousands less than their counterparts on the London Underground.

In some cases, the difference can be an astonishing £27,000 a year despite the roles being equivalent.

The first round of strike action took place over six days in December, following the imposition of a pay offer by TfL which was rejected by the workers as unacceptable.

Thus, the workers will strike again on 20, 21, and 22 February and further industrial action will be scheduled if the dispute is not resolved.

Unite general secretary Sharon Graham said: "TfL's imposed pay offer is an insult to these workers, who play a vital role in keeping the public safe.

"They cannot keep being treated as second class employees compared to their London Underground colleagues.

TfL must come back with an acceptable offer, or these strikes will continue to escalate."

CPOS enforcement officers are responsible for safety and security at Underground, Overground and DLR stations and the London bus network.

Due to their roles preventing violence and aggression, the workers are subject to high rates of verbal and physical abuse.

In the last few months alone, workers have reported instances of being racially abused, spat at, attacked with a bottle, punched and headbutted.

Unite regional officer Steven Stockwell said: "These workers regularly put themselves in physical danger for the security of the public.

"It is totally unacceptable that they are paid less than their London Underground colleagues performing the same role.

"TfL is entirely responsible for this dispute and the impact it will have on the network. It needs to come back with an acceptable offer."