Ukip is on course to come second in at least 100 seats at the general election as it displaces the Tories, Labour and Lib Dems as the main opposition across large parts of the country, according to new analysis of the party’s electoral prospects on 7 May.

The extraordinary potential haul of Ukip “silver medals” – in an addition to a likely tally of half-a-dozen or so seats at Westminster – would represent a massive breakthrough for Nigel Farage’s anti-EU party, which failed to achieve even a single second place in 2010.

The analysis, conducted by Robert Ford at the University of Manchester for the Observer, suggests that the biggest threat to the established parties from Ukip will come in future local and national elections after May, once it has put down local roots and established itself in the minds of voters as a real alternative to the incumbent party.

It also means that the future of the UK in the EU – normally not a top issue on the doorsteps – will become far more central to election debates, as Ukip candidates press the case for the country to quit the EU and apply pressure for an in/out referendum.

Examining Ukip’s strength, as well as byelections in this parliament, Ford concludes that Farage’s party will pile up “silver medals” across industrial and urban regions in the north, as well in parts of the Midlands, the south east and East Anglia and the south west.

The party is polling at between 10% and 15% in most polls. In today’s Opinium/Observer poll it is on 14%.

“At a conservative estimate, there look like being 70 to 100 Ukip silver medals at the election and it could well be more,” said Ford, who co-authored a book on the rise of Ukip – Revolt on the Right – with fellow don Matthew Goodwin..

Ukip currently has two MPs following successive byelection wins for Tory defectors Douglas Carswell in Clacton and Mark Reckless in Rochester and Strood, last autumn. The party is hopeful of winning a handful of others on 7 May, including Thanet South, where Farage is facing a close fight to defeat the Tories.

Ukip’s own strategists believe the party could come second in at least 100 seats in the north alone, as it replaces the severely weakened Tories as the main opposition to Labour, and begins to breathe down the necks of Labour MPs. Ford sees Ukip coming second to several shadow cabinet members including Ed Miliband in Doncaster North, Ed Balls in Morley and Outwood, Yvette Cooper in Normanton, Pontefract and Castleford and Rachel Reeves in Leeds West.

Just as Ukip is on course to replace the Tories as the main opposition in parts of the north, it is set to do the same to Labour and the Lib Dem in parts of the south and south east, and the Lib Dems in the south west.

Ford cites Essex, Kent and East Anglian seats – such as Castle Point, Basildon South and East Thurrock, Thanet North, Sittingbourne and Sheppey and Norfolk South West – as examples of where Ukip is likely to secure solid second places.

In the south west, Ford says Ukip “will be most likely to gain their silver medals at the expense of the Lib Dems in Conservative-held seats” listing Cambourne and Redruth in Cornwall and Devon South West and Bridgwater and West Somersetas examples.Mark Reckless, the Ukip MP for Rochester and Strood, said he believed the estimate of 100 second places for Ukip was too low. He predicted that their second places in the north would be the beginning of a huge transformation in British politics.

“I do not believe the Tories will win enough seats on May 7 to be able to deliver David Cameron’s plan for an in/out referendum on Europe. It will only be when enough of the third-placed Tories join Ukip in the north that there will be a majority in the House of Commons that we need to change Britain.”