Voters in some parts of the country are "all but ignored" by the political parties, a new report has said.
The Electoral Reform Society said MPs sitting on huge majorities were barely challenged by their rivals, while parties spend 22 times more on hotly-contested marginal seats.
The society, which wants to reform Britain's voting system, said many candidates do not even advertise in safe seats, meaning voters often are not moved to go out and vote.
At the last general election, just 14p was spent per individual vote in Bootle, Merseyside, where Labour romped home with 21,181 majority.
By contrast, in marginal Luton South, the figure was £3.07, where Labour just held off the Conservatives.
In the Scottish seat of Motherwell and Wishaw, the major parties did not spend any money at all, the society said, while in almost a third of constituencies no public meetings were held.
The most valuable seats:
Luton South, Aberconwy, Barking, Poplar and Limehouse, Northampton North, Hampstead and Kilburn, Buckingham, Norwich South, Brighton Pavilion, and Bethnal Green and Bow.
And the least valuable:
Bootle, Ruislip Northwood and Pinner, South Leicestershire, Halton, Sheffield Heeley, Knowsley, Leeds East, Ashton-under-Lyne, Makerfield and Beckenham.
Katie Ghose, the society's chief executive, said the "postcode lottery" system meant votes were not equal.
She said: "If you live in a marginal seat, then parties will spend money trying to attract your vote. But if you live in a safe seat – as so many people do – then you will be all but ignored. Our report shows that where parties tighten their belts, people will be much less likely to vote.”
Ghose said the "massive inequality" was turning people off politics.
She called for reforms to political funding so parties have the resources to campaign across the country, and a new electoral system.
However, when the alternative vote system was proposed in 2011, it was overwhelmingly rejected in a referendum.