NHS Information Centre figures for 2007/8 show the average GMS or PMS partner in the South West SHA area earned £96,773 per year before tax.
This is nearly 9 per cent less than the UK average of £106,072 for 2007/8 and 17 per cent less than the highest earners, east of England GPs, who averaged £118,274.
Following an earlier report on GPs' expenses in September, the latest breakdown reveals that single-handed GPs across the UK also earn an average of £20,815 more than in those in practices that have six or more GPs.
The data reveals that rural dispensing practices earn more than dispensing practices in urban locations, but the reverse is true for non-dispensing practices.
Dr Peter Joliffe, chief officer of Devon LMCs, said the high number of part-time partners and female partners may explain low income in the south-west of England.
'It comes down to "how much does a GP want to earn?". I think many GPs in the South West have made work/time choices - lifestyle choices.
'There's no point living in one of the most beautiful places in the country if you have your nose to the grindstone all day.'
GPC chairman Dr Laurence Buckman also defended the above-average incomes single-handers earn, saying they were more likely to work full-time than those in multi-partner practices, and often bear heavier workloads and responsibility.
The data shows partners in Wales were hit with a decrease in pre-tax income of 4.5 per cent between 2006/7 and 2007/8. This is due in part to an increase in the cost of their salaried employees, whose average salary rose by 12.2 per cent that year to £57,408.
The average UK GMS or PMS partner's pre-tax income fell by 1.5 per cent to £106,072 between 2006/7 and 2007/8.
Although gross earnings rose by 1.9 per cent, expenses rose by 4.5 per cent over the same period.
Salaried GP pay continued to rise, reaching £55,790 for those in either GMS or PMS practices, up 3.4 per cent from 2006/07.
- Rate Your PCT: Regional variation in ratings given to PCTs: NHS South West