Dr Daniel Ubani, registered by NHS Cornwall and Isles of Scilly, gave 10 times the recommended dose of diamorphine to a patient in Manea, Cambridgeshire, who later died in February 2008.

Speaking during a Parliamentary debate on out-of-hours on Wednesday, Mr O'Brien said: ‘A general examination of a number of PCTs has shown that some have not carried out the level of tests and checks that they are legally obliged to undertake on a person's ability to speak English. I understand that Cornwall was not carrying out adequate checks but I am told that it is now.'

During the three-hour debate, MPs heard that a problem with the PCT was raised in a Parliamentary debate in February 2007. Truro and St Austell Liberal Democrat MP Matthew Taylor said then: ‘Mr and Mrs T were gobsmacked when their daughter was seen by another overseas agency doctor who not only found it difficult to understand her but relied on an electronic word converter to communicate with the patient.'

Shadow Conservative health minister, Mark Simmonds, added that ‘rumours are circulating among GPs that one or two PCTs have a reputation for giving easier access to the performers list'.

Mr O'Brien added that an out-of-hours review was being undertaken by the RCGP and primary care czar Dr David Colin-Thome. He said: ‘I expect the report to show, among other things, that not only have things improved since 2004, but that decentralised controls on PCTs have led to an unacceptable variation in their enforcement and that more action is needed to ensure that PCTs perform their control obligations.'

Earlier during the debate Mr Simmonds mentioned a GP newspaper story. Referring to GPC chairman Dr Laurence Buckman, he said he ‘has recently been quoted as saying that the prevalent view among GPs is that the Labour party is the enemy of the NHS'.

The out-of-hours review is to be published when an inquest involving Dr Ubani is expected to conclude on Thursday. 

Antek Lejk, the director of partnership commissioning with NHS Cornwall and Isles of Scilly PCT, said: ‘We have strengthened our procedures and require written evidence of English language skills from all applicants to our performers list whose first language is not English. We further require written evidence that applicants will work in our area.'