Ash is joining forces with the Trades Union Congress and the Chartered Institute of Environmental Health to host a campaign conference that will discuss ways of stepping up the pressure on the Government to introduce a ban on smoking in the workplace.
The conference represents the start of a new approach in Ash's strategy.
Until last month, the charity had focused on banning tobacco advertising.
The realisation of that goal has freed it to make protecting employees from the dangers of passive smoking its new priority.
Ash estimates that three million people are exposed to smoking at work in the UK. The three organisations will use the conference on 9 April to call on the Government to implement the code of practice on smoking at work that was first mooted four years ago.
Former health and safety commissioner Baroness Gibson will chair the conference, which will hear from US anti-smoking campaigner James Repace and National Asthma Campaign chief executive Donna Covey.
Ash research manager Amanda Sandford said: "The issue of passive smoking is now very much at the forefront of our campaigning."