The report, by an independent team, says that the crash on 8 August between a crowded commuter train and an empty set of coaches was caused by the failure of the commuter train's driver, a Mr Afford, to stop at a red light.
A journalist, Ruth Holland, was killed in the crash and nearly 20 people were hurt, a dozen seriously.
The inquiry team, headed by David Maidment, a safety consultant, found that Mr Afford, who has been a Watford driver for 34 years, had "six previous operating irregularities on his record, mainly around 1991/2". Three involved braking problems caused by leaves on the line, one concerned excess speed and two, in 1988 and 1992, involved going through red lights.
As a result of these two incidents, he was put on the "driver at risk register" by North London Railways, but as there were no further mishaps this was allowed to lapse.
The report questions whether drivers should be removed from the register as quickly as occurred in this case.
The report also raises the question of undue pressure on drivers. Although a 60 mph speed limit had been imposed, Mr Afford began accelerating after slowing down to 60, the report says. It describes this acceleration as "a puzzle" and says: "An issue for consideration is whether there has been any undue pressure on drivers on punctuality performance that causes them to drive their units with little margin for error in braking."
The report also reveals that the same signal had been passed at red four times in the past two years, a very high figure given there are only 600 such incidents each year on the railways. Local drivers have said that they have been concerned about this area of the track for several years.
The findings of the report will reopen the debate about automatic train protection (ATP), which stops trains automatically if they go through red lights and whose introduction was recommended by the inquiry into the 1988 Clapham rail disaster. Mr Maidment says that ATP would have prevented the crash but accepts the argument that the pounds 400m cost of fitting it throughout the network was prohibitive.
Railtrack confirmed last night that the report had been completed. A spokesman said the recommendations would be acted on.