The Gas Forum, which represents most independent suppliers in the residential and commercial markets, has written to Lord Fraser, Energy Minister, urging the Government to offer competition to a further 2.5 million homes later this year.
Roger Turner, managing director of United Gas and a chairman of the Forum, said the plan was to introduce competition to the whole of Scotland in October.
The move would need an amendment to 1995 legislation which says nationwide competition cannot take place earlier than 1998. The target preferred by TransCo, the pipeline business of British Gas, is for no further trials before next April.
The letter explains: "Technically adding another region during 1997 would require an order to be laid before Parliament and we believe that the government should take this necessary action in the very near future."
Mr Turner said: "It makes so much logistical sense to keep up the momentum. The idea is that we would kick off with another phase comprising Scotland and some of Northern England, though the centre of gravity of the process would still be April 1998."
However, a postscript to the letter said it did not represent the views of three large suppliers: Quadrant, run by Esso and Shell, Mobil and Calortex, a joint venture between Calor and Texaco. Calortex, which claims to have grabbed the most customers in trials so far, described the letter as "irresponsible."
Neil Lambert, Calortex's joint general manager, said he was "frankly very annoyed" by the letter. "We think the next trial should take place as early as possible once the systems run by TransCo are able to handle it. This letter is saying we should go whether the systems are in place or not."
Mr Lambert said he saw no reason to disbelieve claims by TransCo that it needed a crucial few months breathing space to complete new computer systems which would support customer databases to track households as they switched supplier.
Yesterday competition was extended to a further 900,000 homes in Kent and Sussex, on top of the 1.1 million in trials in the South-west of England.