Unions have demanded better protection for frontline rail staff from irate passengers as cancellations and delays continued on the Govia Thameslink Railway and Northern rail lines.

The RMT said numerous platform staff and onboard crew had been verbally abused, taking the brunt of frustration after a new timetable was introduced on Sunday – with the service deteriorating through the week.

Dozens of peak-time cancellations affecting lines around Manchester and London on the first weekday of the new schedule led to widespread anger on what unions dubbed “meltdown Monday”. While train companies appealed for passengers to bear with them during “teething troubles”, an even higher number of services have been disrupted since.

Around half of trains due to run through the upgraded central route in London between Bedford and Brighton were cancelled or severely delayed on Thursday and Friday morning.

Official performance measures for Northern trains improved on Thursday, ironically, due to a strike by RMT guards that meant Arriva Rail North was operating to a reduced strike timetable.

The RMT general secretary, Mick Cash, said: “The vast majority of passengers know that the ongoing timetable problems in the wake of Meltdown Monday are down to the train companies and not the staff, but some lash out from sheer frustration.

“There is no excuse for that whatsoever and the union will not tolerate a situation where our members at the sharp end are effectively being deployed as human shields by a remote and incompetent management.”

The union said it wanted the train operators to take seriously their duty of care to staff, by rigorously enforcing penalties against abusive passengers, and to put up signage saying that train staff were not responsible for the chaos.

Cash added: “After the failure of East Coast, this chaos is the endgame for the rail privatisation experiment.”

The new timetables, which promise to bring more capacity and efficient services around Britain, including a a regular Tube-like Thameslink service through the heart of London, have left tens of thousands of passengers furious.

A lack of properly trained drivers to operate new trains and routes has been blamed. Earlier this week, Chris Grayling, the transport secretary, said Network Rail should bear much of the blame for overrunning work that left train companies insufficient time to plan their changes.

Network Rail and Northern have commissioned an independent into the problems with the timetable change. David Brown, managing director of Northern, said: “We are doing everything we can to minimise cancellations and delays and keep our customers informed. It has been difficult for many of our customers and I am truly sorry for this.

“There is urgent work to do to fully understand what did and didn’t work on all aspects of planning and delivery of the new timetable.”

A Govia Thameslink spokesperson apologised for the significant disruption on Thameslink and Gatwick Express, which he said was “owing largely to the scale and complexity of the timetable changes introduced this week, compounded this morning by an unrelated operational incident at Blackfriars and other incidents on the network”.

He said disruption on Thameslink on Thursday had been exacerbated by other issues, including a signalling failure and a train fault that resulted in a number of cancellations.