TRADE unionists called on the government to bring “certainty” to the railway industry today after a new report said there was no way of knowing how much the final cost of HS2 will be. 

A report from National Audit Office warned yesterday that it was impossible to “estimate with certainty” the final cost of the long-delayed rail project.

Last week, a government-commissioned report claimed that the cost may be to the tune of £106 billion.