Legislation coming into force on Monday will mean that over the next 12 months, unions will have to persuade 6 million of their members to continue having their subscriptions deducted by employers.
John Monks, who takes over from Norman Willis as TUC leader in a fortnight's time, believes the union movement will have to 're-recruit' nearly three-quarters of its members.
Mr Monks said yesterday that it was 'an enormous challenge' and that unless unions responded efficiently and effectively, the movement would be in 'serious trouble'.
He said: 'This will be the top priority for the trade union movement over the next year and it will mean that union activists and officials will have to have 6 million conversations in order to ensure the continued existence of unions.'
Under the provisions of the Trade Union Reform and Employment Rights Act 1993, union members will have to authorise the deduction of dues under the so-called 'check-off' system before August 1994. Thereafter they will have to recommit themselves every three years or the arrangement will cease.
Mr Monks's expression of concern came yesterday as it emerged that at least 40 per cent of the members of the rail industry's biggest union has failed to make a long-term commitment to the organisation. After two 24-hour strikes in the spring, BR withdrew the automatic deduction arrangement for the Rail, Maritime and Transport union. The union has persuaded approximately 60,000 of its members to agree to direct debits from their bank accounts, but 40,000 have yet to sign up. Much union time will be spent collecting subscriptions in cash.
The experience of the rail union could provide a clue to the success of future campaigns within other unions. However, the Transport and General Workers' Union and the GMB general union could be faced with bigger problems because their members are spread throughout thousands of workplaces.
One of Mr Monks's first duties as general secretary will be to draw up a submission to the House of Commons Committee on Employment, which has decided to investigate whether there is any future for unions in Britain. The TUC arguments have to be submitted by 6 October.
Referring to the legislation on check-off, Mr Monks said that there could be some benefits. 'It will mean that unions will have to renew contact with their members, whereas the check-off system did not necessitate it.' He detected a lukewarm response from employers to the new statute. Companies will be expected to ensure that all members using the check-off system have an opportunity to opt out in the next 12 months.
Mr Monks said: 'This is almost certainly the biggest threat to the fabric of unions since Mrs Thatcher came to power. If the union campaign is successful then we could attract new members. If we fail, however, we could be in serious trouble.' He thought the new legislation 'unnecessary' and a further attempt by the Government to undermine unions.