A café in central London has sparked outrage with a sign that ‘banned’ RMT members for entering the premises, but offered a ten per cent discount to all other prospective customers.

The joke posted on the board outside Grill Market read: "NO RMT MEMBERS. 10% off coffee for everyone else" and was widely condemned after being posted on Twitter as the 48-hour tube workers' strike continued.

The Holborn-based cafe was quick to issue an apology on Twitter and stressed the sign was only meant in jest, tweeting: "Again, total apology to anyone offended by the board this morning, was only supposed to be a joke, clearly I got it VERY wrong."

Download the new Independent Premium app Sharing the full story, not just the headlines

But the apology appeared futile, as many responded by describing the joke as "terrible" and in poor taste. Others lambasted the café for "belittling" the plight of workers striking against plans to close Tube ticket offices.

The manager of Grill Market, who gave his name only as Tom, said the sign was not intended to cause any offence and was simply "a really badly judged joke", which has since been removed from the board.

He told The Independent: "Most people who came into the shop seemed to find it quite funny, but reading back it back I realise how it sounds.

"I wasn't thinking about people losing their jobs, it was just to make people smile who were having a bad day."

But some Twitter uses have criticised people for taking the sign so seriously, with many arguing it is simply a joke and should be treated as such.

"Ignore them, it was both funny and appropriate. Well done" was one response while another said it was "a great shame - the board would have got my business," after it was taken down.

The RMT say the closure of ticket offices will cost hundreds of job losses and threaten safety.

Daily coronavirus briefing No hype, just the advice and analysis you need Enter your email address Continue Continue Please enter an email address Email address is invalid Fill out this field Email address is invalid Email already exists. Log in to update your newsletter preferences Register with your social account or click here to log in I would like to receive morning headlines Monday - Friday plus breaking news alerts by email Update newsletter preferences

Shape Created with Sketch. In pictures: Tube strike April 2014 Show all 5 left Created with Sketch. right Created with Sketch. Shape Created with Sketch. In pictures: Tube strike April 2014 1/5 Tube Strike Commuters travel on the Northern Line of the London Underground which is running a limited service due to industrial action on April 29, 2014 in London, England. Getty Images 2/5 Tube Strike Commuters at Stratford Underground, Overground and DLR Station in east London, on the first day of a 48 hour strike by tube workers on the London Underground over ticket office closures. PA 3/5 Tube Strike Commuters prepare to travel on the District Line of the London Underground during strike action on 30 April, 2014 Getty Images 4/5 Tube Strike Commuters attempting to board a full underground train on day two of a 48 hour underground train strike on 30 April, 2014 Getty Images 5/5 Tube Strike Commuters wait at Victoria tube station for limited service trains in London, Britain, 29 April 2014. EPA 1/5 Tube Strike Commuters travel on the Northern Line of the London Underground which is running a limited service due to industrial action on April 29, 2014 in London, England. Getty Images 2/5 Tube Strike Commuters at Stratford Underground, Overground and DLR Station in east London, on the first day of a 48 hour strike by tube workers on the London Underground over ticket office closures. PA 3/5 Tube Strike Commuters prepare to travel on the District Line of the London Underground during strike action on 30 April, 2014 Getty Images 4/5 Tube Strike Commuters attempting to board a full underground train on day two of a 48 hour underground train strike on 30 April, 2014 Getty Images 5/5 Tube Strike Commuters wait at Victoria tube station for limited service trains in London, Britain, 29 April 2014. EPA

But London Underground (LU) maintains that staff would be better employed on station concourses as only three per cent of tickets are bought at ticket offices.

If the dispute is not resolved, RMT members say they will stage another walkout - this time for 72 hours - from 9pm on Monday 5 May.