Liberal Democrat leader Nick Clegg today dismissed Labour promises to overhaul the voting system, likening them to a "consumer guarantee from Del Boy".
Gordon Brown is expected to use a keynote campaign speech to highlight Labour's plans for constitutional reform - including a referendum on introducing a form of proportional representation for Westminster.
The proposal has widely been seen as an attempt to woo the Liberal Democrats in the event of a hung Parliament - although Labour's plans do not go as far as the Lib Dems would like.
However Mr Clegg insisted that neither Labour nor the Conservatives could be trusted when it came to issues of constitutional reform.
"They have systematically at every turn blocked every single reform - they have blocked party funding reform, they have blocked reform on lobbying," he told the BBC Radio 4 Today programme.
"Believing any promises from them on political reform is a bit like accepting a consumer service guarantee from Del Boy - don't believe it, they are trying to treat you like fools."Reuse content