A letter sent to local NHS bodies has instructed them to improve people's access to and choice of GPs.

It says using alternative providers from the private sector should be considered.

According to The Times, the letter - from Department of Health Commissioning Director Mark Britnell - was altered before being issued, with references to "competitive tendering" toned down.

However, doctors' leaders insisted the final version remained "very aggressively worded".

Doctors were allowed to opt out of some of their work commitments, including providing night and weekend cover, under the revised contracts introduced by the Government in 2004.

The measure was among the most controversial elements of the reforms, as around nine out of 10 took up the option, leaving patients struggling to get appointments out of normal working times. Meanwhile, average annual pay for GPs has soared above £100,000.

Mr Britnell's letter reportedly tells primary care trusts to come up with plans to persuade doctors to "respond to the needs and expectations of their patients, for instance by opening practices for longer periods".

It also apparently suggests that trusts make "full use of existing contractual arrangements and other mechanisms" - the passage said to have replaced the reference to "competitive tendering".

Dr Laurence Buckman, chair of the British Medical Association's GP committee, told The Times: "It is a very aggressively worded letter which I don't think can be interpreted in any other way but as giving primary care to the private sector."