A second cabinet minister has urged Gordon Brown to hold a referendum on electoral reform to regain the political initiative.

John Denham said designing a system in which "every vote counts" would help rebuild the trust between MPs and their electors following the expenses scandal.

His call came after Alan Johnson, the Health Secretary, argued that the issue should be put to the vote at the next election.

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Mr Denham, the Secretary for Innovation, Universities and Skills, told The Independent: "One of the ways we can reconnect politicians with the voters is to increase the power of the voters. Letting people choose the electoral system would be a huge step forward."

He added: "The background ... is the need to look for ways of re-establishing better trust between the voters and the political system. Because of that, it takes on added potency and urgency."

Up to 100 Labour MPs could support the referendum plan. The issue of proportional representation has been on ice within Labour ranks for a decade.

But supporters say the expenses furore – and the possibility of a hung parliament after the next election – could give it new momentum. They are planning a Commons motion next week to gauge the extent of support.

John Grogan, chairman of the Labour Campaign for Electoral Reform, said: "The political kaleidoscope has been completely shaken up in the last few weeks."

However, the majority of the Cabinet is thought to oppose discussion of electoral reform. Senior figures such as the Justice Secretary Jack Straw believe trust will be better restored by reform of the Commons. Denis MacShane, the former Foreign Office minister said PR allowed extremists into Parliament.