In an interview with the Guardian yesterday, Unite's general sectretary Len McCluskey suggested taking action during the sporting event would be justified due to the current problems faced by public sector workers being "so deep and ideological".
The statement emerged after the RMT confirmed it is in dispute with Transport for London (TfL) over the pay that London Underground staff will receive across the period of the Olympics and also comes against a backdrop of continuing concerns over issues including austerity cuts, public sector pension reforms and reforms to the NHS
RMT has told TFL that it is "appalled" that the employer intends to restrict annual leave over the Olympic period, including banning annual leave during the Games in at least one department.
The union says the plan will make life impossible for many staff, for example those with school-age children. RMT is also "similarly appalled" at TfL's totally "inadequate financial offer to members", consisting of a £15 payment if a shift is changed.
As a result, RMT says it has no option but to organise a ballot for industrial action of all members in departments of TfL for strike action and for action short of strike.
RMT's executive has also considered again the lack of progress from London Underground in reaching an acceptable agreement with the union over the Olympics recognition and reward issue and has agreed to formally declare a dispute with London Underground on this matter.
RMT General Secretary Bob Crow said: "RMT reiterates our stance that all grades of transport employees are entitled to a decent financial reward for their efforts transporting huge numbers of passengers during the Olympics and are entitled to take leave during the summer. Working conditions and important agreements should not and need not be attacked in order to facilitate Olympic running."
Tom Flanagan, national head of employment law at Irwin Mitchell, said it may prove difficult for any planned industrial action during the Olympics - whether by a single union or as part of co-ordinated action involving several bodies - to be blocked.
He said: "It is possible that unions could lawfully call a strike during the Olympics, as long as they meet legal requirements for calling a ballot.
"The prerequisite for calling a strike ballot is that the relevant employees have a genuine "Trade Dispute" with their employer. The case of RMT's arguments over additional wages would probably such an example, although there is some indication that this is being engineered in order to be able to call action during the Olympics.
"However, some other reasons for action suggested in recent days, like opposing the proposed reform of the NHS, would probably not be classed as a trade dispute in other sectors, particularly the private sector."
"Having established that there is a genuine Trade Dispute, unions would then need to comply with the various rules governing strike action ballots, such as making sure that the correct people are allowed to take part in the ballot, then in the strike and ensuring that notices are given in time and in the proper form. Those requirements are for the protection of employees, as well as giving help to employers, because without them, the employees would be acting in breach of their employment contracts. There is, therefore, a strong obligation on unions to make sure that they get it right.
"Such moves are bound to revive calls for changes in the law on ballots, particularly to include some of the requirements which have already been debated at length.
"These include suggestions setting a minimum turnout of 40 per cent or proposing that at least 50 per cent of all members must vote in favour of action - not just the majority of people who actually vote. Such issues are raised from time and time as there is an argument that the country, or in this case major global events, should not grind to a halt due to the action of a relatively small number of workers.
"There have also been statements by unions about the 'right to association'. This references the argument that UK strike laws are in breach of Article 11 of the European Convention of Human Rights, a point which is being taken by unions to the European Court of Human Rights at the moment.
"This is an example of how unions, at least as much as employers, are now using law as their means of conducting industrial relations."