In a letter to the Review Body dated 19 December, the health secretary undercut a 2 per cent rise recommended by the Treasury (GP, 2 December).
The BMA this week criticised 'government meddling' in the pay review.
BMA leaders are also angry that Ms Hewitt's letter referred to a '0 per cent inflation uplift for the GMS contract'.
In a letter to the Review Body dated 6 January, BMA chairman James Johnson urged it to ignore 'repeated intervention from ministers' which subjected it to 'unacceptable pressure'.
The Review Body's report is expected at the end of February.