A new book has revealed that Ukip considered forming a pact with the BNP six years ago, with two members of the party's national executive committee at the time in favour of the idea.

In 2008 Nigel Farage acknowledged that the BNP had proposed a deal for the European elections the following year, but insisted it had been unanimously rejected. Farage told reporters then: "I'm simply amazed that the BNP thought we would even consider such a thing."

Now the new book, Revolt on the Right, by Dr Matthew Goodwin and Dr Robert Ford – called the most definitive account yet of the Ukip movement – reveals that the BNP's proposal was canvassed among 17 members of the party's NEC. Two members supported the proposal, it has emerged.

Farage, who said he had been against a pact, told the authors: "There were a lot of people saying to me at that time, 'You've got to do a deal with them.' I even had Tory MEPs saying to me, 'Nigel, you've got to do a deal with these people.' We were being beaten by them regularly in local elections. So there was huge pressure on me. The nature of the deal was the BNP would stand in some regions in the European elections in the north, and Ukip would stand in the south, and that would be the electoral pact: we wouldn't oppose each other."

Of the members who offered support for the pact, Farage said: "They were the angry old men of old Ukip who thought Ukip was doomed."

The political predicament of Ukip in 2008 contrasts with its potential today, the authors say. In the book, published this week, they say the party has emerged from the crash with the potential to attract a third of the electorate.

Around 30% of voters are now believed to be both Eurosceptic and opposed to immigration, or Eurosceptic and politically dissatisfied, the defining themes for Ukip. Such sentiments are continuing to grow in strength among the electorate, according to the authors, who draw on the biggest pool of data so far amassed on the political movement.

The book provides evidence that the share of voters holding Eurosceptic views and at least one other radical right belief has increased by five to seven percentage points since 2008. Ukip is widely seen as not having a credible manifesto and has faced serious questions about the calibre of its MEPs, the authors note.

This weekend, the party was dogged by claims that it had misused EU funds in paying staff working in the UK. Yet Goodwin, from Nottingham University, and Ford, of Manchester University, say the "army of potential supporters for Ukip is growing in size" and is being aided by continued anger at Labour's record and disaffection with the Tory leader.

They argue that Farage and Ukip face huge challenges in the first-past-the-post electoral system, and given the party's continued unpopularity among women, ethnic minorities, graduates and the young. However, Ukip is now the favoured electoral option among those who strongly disapprove of the EU – 20% of all British voters.

Over the past three years, the party has also performed better than Labour among older, working-class voters and those who are struggling financially. The party is using tactics similar to those once successfully deployed by the Lib Dems, the authors say, in that they seek to deepen their vote in particular areas by getting into local councils and building strongholds.

It is claimed that, of the five constituencies where Ukip stands its best chance of general election success, four are Labour seats (Great Grimsby, Plymouth Moor View, Ashfield and Walsall North) and one is Tory (Waveney). The consistent feature in these areas is a splintering of the traditional vote and the existence of a large, older, blue-collar demographic.

The book suggests that the potential for Ukip's rise can be clearly seen in societal changes that developed decades ago. The authors write: "Its seeds lay among groups of voters who struggled with the destabilising and threatening changes brought by deindustrialisation, globalisation and, later, European integration and mass immigration."

The academics claim Farage is fusing three issues to make a coherent message: "Farage's party now encourages voters to say 'no' three times: no to the Eurocrats in Brussels and Strasbourg; no to the politicians in Westminster; and no to immigration. This is not a grand ideological vision – there is no 'Farageism' – but it is a coherent and highly effective message."

They add: "Ukip is not a second home for disgruntled Tories in the shires; it is a first home for disaffected working-class Britons of all political backgrounds who have lost faith in a political system that ceased to represent them long ago."