When MPIG goes, the per-patient pay gap between England and Wales will rise from 9 per cent to 11.2 per cent.
Practices in Wales lost £6.80 per patient from their global sums when the original 2004 Carr-Hill formula was changed, so they were compared with Welsh practices alone rather than with a UK mix.
In 2008, matched Welsh practices received 9 per cent less per patient than practices in England.
'Phasing out the income protection ... means ... the relative income deficit will grow from 9 per cent to 11.2 per cent,' GPs Dr Gwion Rhys and Dr Hank Beerstecher say in a study published in BMC Health Services Research.
'It would seem immoral to offer different payments to various contractors providing identical services,' Dr Rhys and Dr Beerstecher comment.