But supporters of reform were confident that the decision accurately reflected the mood for change in the party as a whole, which is due to debate the issue at the autumn conference. Some Shadow Cabinet members and MPs will take their cue from John Smith, the party leader, who will declare his views after the NEC meeting. But the debate in the party - and the conference decision - will cover much greater ground.
Some unions have already declared themselves to be in favour of change, while others were waiting for the commission headed by Professor Raymond Plant, the Labour peer, to produce its conclusions.
There were also indications yesterday that a 'three-horse' contest could emerge as the debate continues - between first-past-the-posters, supporters of the supplementary vote (SV) system and supporters of an 'additional' or mixed member system (MMS). While SV aims to ensure winners get as near to 50 per cent of constituency votes as possible, MMS involves topping up constituencies with MPs selected from regional lists.
MMS would achieve greater proportionality, but SV would maintain all MPs' links with a constituency.
Lord Plant's commission narrowly opted for SV on Wednesday night. But commission members who support MMS pledged yesterday to continue to campaign for it. Jeff Rooker, the MP for Birmingham Perry Barr and chairman of the Labour Campaign for Electoral Reform, said neither first-past-the-post nor SV tackled regional imbalance.
Under SV any candidate with more than 50 per cent of first preferences is elected. If no candidate achieves more than 50 per cent, all but the top two candidates are eliminated. Of these, the candidate with the most first and second preferences is elected.
Dale Campbell-Savours, Labour MP for Workington and creator of the SV system, said he believed many opponents would change their minds after mature reflection.
Mr Campbell-Savours said his system was not designed to produce coalition governments. 'You get majority governments with first-past-the-post but you are just as likely to do so under SV.'
Mr Campbell-Savours said 58 per cent of the public had voted against the Conservatives in the last election. 'What SV does by applying greater proportionality to the system is remove the in-built bias to the Conservatives which we've now had for four general elections,' he said.
Bob Cryer, chairman of Labour's Campaign for First Past the Post, warned the NEC that if it even considered any form of proportional representation, it would be 'wrapped round their necks at the next general election as an admission of defeat'.
But Mr Rooker said: 'When anybody seriously considers electoral systems they reject first-past-the-post.'
Mr Rooker said he was disappointed that the commission had rejected MMS, saying SV would damage Labour because the party would be wiped out in the South. 'SV is OK, but we need the top-up,' he said.
Mr Rooker predicted that 'the penny would drop' within six months. 'People will say, SV is great but it needs the top-up.'
The Liberal Democrats support the single transferable vote (STV), which would involve the creation of large multi-member constituencies.
But some senior Liberal Democrats, aware of the need to cut down disagreement between the two parties, are increasingly indicating that a 'top-up', or additional member system might be acceptable. Like MMS, it would involve selecting extra MPs from lists to increase proportionality.
One source said yesterday: 'The 'list' element need not involve selecting the extra MPs by party officials.' Priority could be given according to the proportion of votes obtained by unsuccessful candidates who stood in the election, he said.
Letters, page 19