Publication of GP income should not include private work, the GPC has said.
The warning comes after it was revealed that GPs are likely to be one of the next professions to have their incomes disclosed.
A spokesman for the Cabinet Office said last week that this is the direction of travel for the new government, which hopes the transparency agenda will 'win back people's trust'.
GPC negotiator Dr Chaand Nagpaul said it would be 'wholly inappropriate' to publish GP earnings that included private income.
He said: 'The only income of relevance to the public is the proportion of income GPs earn as NHS income.
'If government is even to consider this, what needs to happen is a disaggregation of GP income into what is funded by the taxpayer and what is private income.'
Dr Nagpaul added that there would also have to be a 'meaningful definitions' to allow like-for-like practices to be compared.
'Many GPs supplement work through out-of-hours or taking on additional roles,' he said.
In its coalition document, the government said it would need to 'throw open the doors of public bodies'.
The document outlined that the government would require 'full, online disclosure of all central government spending and contracts over £25,000'.
'We recognise this will help to deliver better value for money in public spending, and help us achieve our aim of cutting the record deficit,' it said.
The move follows last week's release of the list of 171 public workers earning more than £150,000, which placed DoH chief executive David Nicholson, who earns almost £260,000, in second place.
A spokesman for the Cabinet Office said: 'The publication of the list (of public sector workers earning more than £150,000) just covered civil servants.
'There is a transparency commitment to cover all public bodies. This is the direction of travel, but it will require consultation with staff.'