It is “selfish” and “immoral” to oppose voting reform just because “it has traditionally handed you power”, the co-leader of the Green Party has said.
Caroline Lucas was speaking in a debate on proportional representation being used for future general elections.
The Westminster debate was prompted by more than 100,000 people signing a petition calling for voting change.
The government says the 2011 AV referendum shows the public do not want to change first-past-the-post.
Calling on the Labour Party leadership to support voting reform, Ms Lucas said “it is selfish to continue championing a voting system just because it has traditionally handed you power…. it is immoral when millions of people are disenfranchised as a result”.
Cat Smith, Shadow Minister for Voter Engagement and Youth Affairs, said Labour were “committed to taking radical steps to ensuring all voters are both registered and able to use their vote.”
However she said “changing the voting system alone does not fix the disconnect that is felt by some voters with regard to our political process”.
Under first-past-the-post the candidate who receives the most votes in a local constituency wins a seat in the House of Commons.
This means the number of seats each political party wins does not necessarily reflect its share of the vote nationally – in 2015, for instance, UKIP picked up 3.9m votes but only won one seat.
Under proportional representation, parties’ seats in parliament would be allocated in proportion to the number of votes cast for them.
Ms Lucas admitted she had a “vested interest” in the debate.
In the 2015 general election one million people voted Green and under a proportional system the party could have won 20 seats, she said. Instead the party got just one.
“As a country we pride ourselves on our strong commitment to democracy and yet the vast majority of votes cast don’t make an impact on the overall result,” she said.
She added there was an “irony” that despite leaving the EU “all those who were promised they would be given back control simply will not have it without meaningful electoral reform”.