Mr Lansley has asked NHS chief executive Sir David Nicholson to write to PCTs warning them not to block GPs sending patients to diagnostics when clinically valid.
A DoH spokesman said it was 'unacceptable' to deny access to treatment to hit financial targets alone.
It follows an exclusive GP investigation that found GPs face heightened scrutiny over use of diagnostic scans. Some trusts had scrapped direct access to scans such as MRI and CT to save costs.
Now, Sir David's letter will say that in cases where PCTs are trying to reduce referrals they should do so on a one-to-one basis, where patients understand the clinical circumstances.
A DoH spokesman said: 'If PCTs are 'banning' GPs from referring patients for scans directly that is wrong and we have already set aside £750m to help them do so.'
He continued: 'In future, this is exactly why we will be giving GPs control of the purse strings. They are more accountable to their patients and they will get rewarded for the standard and quality of care their patients receive.'
Yesterday, Mr Lansley told a joint NHS Alliance and National Association of Primary Care event in London: ‘One of the benefits of moving decision making closer to patients is that GPs are able to make decisions for clinical reasons.
'It is a better way of managing resources to think about the needs of individual patients.’
GP leaders had warned restricting access to scans could delay diagnoses.
- From the Editors blog: GP commissioners put a spring in the step of health secretary Andrew Lansley