A report by the think tank, due next month, will urge managers to make a frank case for restructuring - by admitting that without it, some services will remain unsafe.
Speaking at an HSJ conference in London, research fellow Joe Farrington-Douglas said: 'The conspiracy of silence of the safety of local hospitals needs to be broken.
'At the moment, there's a myth of safety. Patients think their local hospital is safe because we don't say 'look at the poor-quality services we're getting'.'
The report, The Future Hospital: the politics of change, is based on interviews with clinicians, managers, the public and patients in areas facing hospital shake-ups.
It found that clinicians and managers favoured the changes mainly because they felt present services were unsafe. In particular, hospitals were not attracting enough patients and over-relying on locums and agency workers because they could not find enough staff for multiple sites.
But the public rarely hears these fears, the report claims.
Mr Farrington-Douglas told HSJ: 'Managers said reconfiguration would improve things but not that people are dying unnecessarily because they're being seen by non-specialist clinicians.
'They don't want to worry the public, and it goes against their instincts to say services they're delivering aren't high quality. But if they're going to win the debate locally, they have to be honest.'
The report also recommends that more clinical staff be used to convince the public of the need for change. Frontline staff - the most trustworthy group in the eyes of the public - were not fully engaged in the process, the research found.
And often, only the most senior clinicians were drafted in for back-up at community meetings and to front consultation leaflets.
Without the support of other staff, the changes were widely perceived to be motivated solely by financial expedience. 'Clinicians are more trusted than managers but the tendency is to engage senior clinicians such as the medical director,' said Mr Farrington-Douglas.
'The public and patients are also sceptical about top clinicians and feel they might have their own motives for changing hospitals.'
'The engagement needs to be with frontline staff, who are a much more effective conduit of public opinion.'
National emergency access director Professor Sir George Alberti, also speaking at the conference, said clinicians 'have got to stick their heads above the parapet'.
He added: 'Many consultants think it will improve public care - well get up and say so.
'Some of them don't want their cosy lives disturbed. There seems to be a lack of any commitment to improving care.'