Love him or hate him, Lord Ashcroft has developed a reputation in recent years for producing interesting polling data. Today he published the results of a survey of Unite members (712 to be precise, a relatively small sample but enough to give a less than 4% margin of error) on a range of issues.

Many reports on the poll have focused on the risks it exposes for Labour as it seeks to reform its relationship for the unions. As a reminder, Miliband has proposed that in future, union political levy-payers should choose individually to opt-in to affiliating with Labour, rather than choosing to opt out. Given that the current system generates about £8m for the cash-strapped party, it was clearly a bold step.

Ashcroft’s polling seems to confirm the immediate financial risks. It found that just one in eight Unite members polled would pay to join Labour as an individual member, if not automatically signed up as an affiliate. It might be assumed that Unite would make significant one-off donations to the Labour Party to offset any decrease in affiliation fees. But as Ashcroft notes, there are factors that might deter such donations. Firstly, members are highly divided on the issue – 46% said they disagreed with the unions’ donations of £12m to Labour since the 2010 election, with 43% in favour. The figures harden further when members were asked whether they would support such donations in future.

On the face of it then, the polling gives Labour cause for nervousness. But it also hints at difficulties for the Conservatives, mainly because it is a reminder that union members are far from homogenous political block. 23% polled said they would vote Conservative in an election held tomorrow. Another 12% said UKIP. Union members are not in short sure-fire Labour voters. But the Conservative leadership’s current approach – which might politely be characterised as ‘union-bashing’ – is not likely to win further votes amongst members, and risks eroding what support the Conservative party does have.

David Cameron has gleefully used every opportunity at PMQs to talk of Unite and its relationship with the Labour party. The risk for the Conservatives is that this approach, in reality or perception, drifts from bashing union leaders to bashing the unions, and union members, themselves. Some Conservatives have been alert to this risk. Robert Halfon in particular – already known for his popular campaign to freeze fuel duty and calls for ‘white van conservatism’ – has pushed for a different approach, publishing a pamphlet last year called ‘Stop the Union Bashing’. Halfon, and some of his colleagues, see that many union members are the kind of ‘strivers’, to use George Osborne’s language, that the Conservatives need to attract. This is unlikely to happen when a perception exists that the Tory leadership regards the unions – and by extension their members – as an enemy.

The Falkirk debacle has undoubtedly helped the Conservatives. It may have contributed to a small bounce in the polls, and has certainly given Tory MPs a renewed confidence going into the summer recess. But the party must be careful with its rhetoric. As Ashcroft’s polling shows, union members are not a homogenous group. Too much union bashing may raise Tory cheers at PMQs, but at the risk of alienating a significant share of the electorate.