At the end of April, HMRC stopped a long-established practice called 'check off', whereby union dues were automatically taken off payroll for employees who wished to belong to a union, without the need for the employee to take action to set up a special payment via their bank account.

PCS, which currently represents around 50,000 HMRC staff, has been running a campaign since the beginning of the year urging its members to switch to direct debits in order to ensure they pay their union subscription regularly.

The union says that around 70% of its members have already done this and has set up a dedicated webpage and phone line to support staff to do so.

In March, a newly formed organisation, called R&C Trade Union (RCTU) launched a website and is campaigning to recruit members from HMRC administration level through to Grade 6.

RCTU has been formed by a group which includes an ex-PCS official and says its creation is in reaction to what it calls the current ‘disarray and decline’ in the trade union movement in the civil service.

Margi Rathbone, RCTU secretary, states on the organisation’s website: ‘Ordinary union members are fed up with politically driven protest strikes that gain nothing but the loss of pay - they are showing their disdain for politically-inspired conflict by demanding change. We are bringing that change - constructive dialogue to get the best deal possible for our members, HMRC and the taxpayer.’

 For its part, on its website PCS claims that one member of the group is an ex-PCS official who was expelled from the union last year following allegations of bringing the union in to disrepute.

RCTU says it is currently representing staff ‘on an individual basis’ and claims to be involved in a number of complex personal cases. However, until it has a larger body of members it will not be able to approach HMRC to seek collective bargaining rights in order to be able to represent its members on the terms and conditions of their employment.

A spokesman for PCS said: ‘HMRC staff need to be represented by a strong, independent trade union with a track record of standing up for workers and fighting for better pay, jobs and working conditions. That's what we do and will continue to do.

‘As well as re-signing tens of thousands of people up to pay by direct debit - a massive task in itself - we are also recruiting new members and we're more than confident we'll emerge from this with a stronger union, ready to face whatever challenges the new government throws at us.’

An HMRC spokesperson said: ‘We are aware that RCTU has registered as an independent trade union and that they are seeking to recruit members in HMRC. HMRC continues to recognise two trade unions, PCS and ARC.

‘In respect of the emergence of RCTU, HMRC's position is one of neutrality and we have neither encouraged nor discouraged RCTU. Employees are free to join a union of their choice and, under current legislation, an employer is obliged to allow any union to represent a member in any personal case. HMRC has advised PCS, ARC and RCTU that there are no plans to grant further recognition to RCTU.’