They pointed out their administrations had been responsible for enacting Britain's first UK safety and health statute: the Health and Morals of Apprentices Act 1902. They also claimed credit for successive factories acts and for drafting the Health and Safety at Work Act in the early 1970s -- though it was passed into law by a Labour government.
The opposition parties were looking for assurances that the raft of employment rights that apply directly from EU regulation, such as those on working hours and parental leave, would not just transfer into UK law at the point of Brexit, but would be maintained once they are purely a matter of UK discretion.
The issue of what is the right level of worker protection in law is a perennial argument between and even inside political parties. There is no universally agreed balance between what society perceives as guarantees of fair treatment and security for employees, and the curbs on business that high social charges or constraints on hiring and firing workers bring.
It's a debate that is likely to become more charged as the post-Brexit settlement emerges and Britain has to decide how it will market itself for inward investment from foreign corporations in the decades ahead.
A recently concluded study by the Centre for Business Studies (CBS) at Cambridge University has analysed economic performance and the pace of labour regulation in 117 countries over 44 years. The CBS data shows a positive match between high rates of economic expansion in developing countries, and adoption of worker protection laws and creation of enforcement bodies. This undermines the notion that a "race to the bottom" in employment rights makes for labour market flexibility that boosts economic growth.
Of course, the positive correlation between individual rights and prosperity is likely to have an upper limit. And where that falls will continue to divert politicians.
Most UK practitioners would probably agree that the safety and health elements of their country's labour regulation is pitched at the right level -- even if they feel that individual regulations, such as those governing construction safety, are ripe for further reform.
The results of IOSH's five-year research programme looking at the profession's place in a changing business landscape (p 42) suggest that the state of regulation should not be the main focus of OSH professionals' attention anyway. The research casts legal compliance as a bedrock on which practitioners can build to secure business and reputational gains for their employers through better -- and smarter -- means of protection, based on a deeper understanding of organisational objectives.
The studies issue calls to action that will inspire some and daunt others, but it offers an alternative to the passivity of waiting for parliamentarians to plot your course.