New voting system 'would have given Lib Dems four more seats'

Nick Clegg's party would have beaten Labour in Hull North and Sheffield Central – where they narrowly lost out in May – if the first-past-the-post system had been ditched in favour of the Additional Vote (AV), where candidates are ranked in order of preference.

The Tories would also have missed out on Harrogate and Knaresborough, where they overturned a massive Lib Dem majority to win back a seat once considered True Blue.

But the most surprising conclusion of the study by political experts at the University of Essex is that Lib Dems would also have won Colne Valley, a seat previously held by Labour and where, although Mr Clegg's party managed to come second they were still left 5,000 votes behind the Tories.

The study by Professors David Sanders and Paul Whiteley – based on information provided in a survey of 14,000 voters – comes as the coalition Government pushes ahead with plans for a referendum next May on introducing the AV system, something the Lib Dems have been pushing for to make the voting system fairer.

"Our detailed research for the British Election Study at the University of Essex suggests that AV would have cut 22 MPs from the Conservatives ranks, and a net total of 10 MPs from Labour," said the experts.

"This outcome would have radically changed the arithmetic of post-election coalition formation. In effect, the Liberal Democrats would have been able to form a majority coalition with either Labour or the Conservatives."

The study shows changing the voting system – which the Tories will campaign against in the referendum, and which stops short of the Lib Dems' desire for a fully proportional system – would have had a significant impact on the political landscape of Yorkshire in May's election.

Colne Valley was one of the Tories' must-win seats having been held by Labour since 1997.

The Lib Dems hoped to pull off a shock victory as popularity in the polls soared following the televised leaders' debates – with Mr Clegg even visiting – but Tory Jason McCartney won with a comfortable majority of 4,837 .