Tony Boorman, Offer's director of supply competition, told a conference of industry executives that the six-month timetable, which would see all 23 million customers able to shop around for electricity by September 1998, was tight but fully achievable.
Commenting on the private protests by some of the regional power suppliers at the speed of the move to competition, he said: "Certainly it is a very challenging programme ... but I don't think on the other hand we should over-egg this pudding.
"It is a change which should come as no surprise to anyone as it was there for all to see in 1989 when the industry was privatised."
He also vented his frustration at the legal challenge, which was made public in a leaked letter from the law firm Herbert Smith, which is acting for the 12 regional electricity companies (RECs) and two Scottish power producers.
He told the gathering: "It's a rather tedious aspect of the industry that members tend to leak things.
"There's a natural reaction to overstate rather than understate the problem."
The letter, dated 19 November, said it would be unlawful for the regulator, Professor Steven Littlechild, to proceed with competition if the system had not been fully tested by April 1998.
Professor Littlechild has turned down industry requests that the process be phased in over 18 months, instead setting the six-month timetable towards full competition, a transition which companies have estimated will cost between pounds 500m and pounds 1bn.
Mr Boorman said he would be meeting with Herbert Smith in a few days' time to try to resolve the objections, but there was nothing in the letter which was of such concern that it could not be sorted out.
In particular, he insisted there was no serious difficulty over concerns that suppliers operating outside their own franchise area would be unable to recover unpaid bills.