You need to look at The National Access and Scaffolding Confederation (NASC). They provide some free advice and design standards for scaffolding ranging from generic to full structural. I am sure there is something on stairs but you have to be a member to view them or you have got to purchase them. I would push it back on your scaffold contractor. Check they are a member of NASC and ask to see the design standard. However if you are using a small company they are probably not members so you need to check their qualifications. There are different levels of competency which allow them to seft design and erect defined types scaffolding. Scaffolding is not just simply scaffolding and a lot of it has to be designed. You have not given any details about the job but most scaffolding stairs come prefabricated. However you could look at Section K” of the building regulations for some guidance. You probably are aware but for others, remember the statutory inspections.

I was looking for specific information in order to be able to push it back to the scaffold contractor and the information appears to be within TG20 which is not freely accessible and is somewhat expensive when its a one off quick reference that is required. Good guidance in building regs part K which are available freely. What we have appears to be compliant so thanks for the answers guys.