Referrals in England rose from 7.1 million in 2003/4 to 8.6 million in 2007/8, but the proportion made by GPs fell, from 68 per cent to 62 per cent, researchers found.
Health data analysts CHKS found referrals from consultants, A&E and other sources rose 32 per cent in this period.
GPs have been accused over the past year of over-referring as PCTs found outpatient appointments rising inexplicably.
Some PCTs began paying GPs to cut referrals, prompting a BMA warning this month that GPs should avoid the schemes (GP, 6 February).
The CHKS study also showed that the proportion of consultants' referrals varied between trusts from 1-60 per cent.
Dr Paul Robinson, head of market intelligence at CHKS, said the consultants' referrals should be monitored closely.
'Nearly a fifth of referrals are from consultants. That is a lot of referrals the commissioner has no control over.'
Many people could be referred to services in primary care or community settings, added Dr Robinson.
Wessex LMC chief executive Dr Nigel Watson, who has also researched the recent rise in referrals, said work was under way to make sure consultant referrals were appropriate.
'The work we did showed there are many factors to explain the rise in referrals, and GP referral is just one factor.
'In one trust, consultant to consultant referrals had risen by 600 per cent,' said Dr Watson.
GPC negotiator Dr Beth McCarron-Nash said the research was 'surprising, and good news'.
'It does seem like GPs are the scapegoat for everything,' she added. 'GPs can contribute by reviewing their referral patterns but I personally don't agree with GPs' income being linked to reducing referrals,' she said.
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