A trade union representing cleaners, security guards and receptionists who work at the Ministry of Justice is preparing to sue the lord chancellor for unlawful discrimination as its members gear up for a three-day strike over pay.

Around 50 security guards and receptionists represented by union UVW will stage a three-day strike in January. They will be joined by around 20 cleaners who went on strike for three days in August. The workers are demanding to be paid the London living wage of £10.55 an hour, and to have parity with civil servants over sick pay and annual leave allowances.

UVW has told the Gazette that it will also lodge a claim in the employment tribunal or High Court over the ministry's outsourcing structure. The union argues that the ministry has breached its public sector equality duty under the Equality Act 2010 because nearly all cleaners, security guards and receptionists are BAME (black, asian and minority ethnic) or migrant workers.

UVW says it will coordinate its strike at the ministry with outsourced workers at the Department for Business, Energy & Industrial Strategy who are members of the PCS union.

The national minimum wage is currently £7.83 for workers aged over 25. The London living wage is £10.55.

The ministry was questioned by Labour MP Catherine West about how much the department pays staff inside and outside Greater London at a rate below the UK living wage, which is sometimes referred to as the 'real living wage'.

In October, justice minister Edward Argar replied that all MoJ employees are paid at least the national minimum wage and national living wage. Argar said the UK living wage and London living wage are voluntary rates set by the Living Wage Foundation: 'These are not statutory figures which relate to the government policy in this area, and so are not legally binding on employers.' 

In Greater London, the ministry has 395 staff paid at a rate below the London real living wage. Outside Greater London, the ministry employs 1,479 staff  paid at a rate below the National real living wage.

A spokesperson for the ministry told the Gazette: 'The support staff at the Ministry of Justice are valued colleagues. The independently advised National Living Wage has helped to deliver the fastest wage growth for the lowest paid in 20 years and the most recent rise in April meant full-time workers will earn an extra £600 a year. We strictly enforce the National Living Wage in all our contracts.'