Even by the Tories' Machiavellian standards, the decision to use the new lobbying bill to crack down on trade union funding of Labour is a remarkably cynical manoeuvre. Under the move, reportedly  the brainchild of George Osborne, measures will be introduced to include union funding of leaflets in election spending limits and to end self-certification of union membership. At present, only the marginal cost of the printing counts towards a party's spending cap but under the Tories' proposals, the full costs, including staffing and premises, will have to be declared. The new law will apply to those organisations "directly affiliated to political parties and those contributing £100,000 a year or more to political parties" (the unions, in other words), while excluding the Conservatives' large business donors.
What this has to do with the latest lobbying scandal, which saw Patrick Mercer resign the Tory whip after allegedly receiving cash for questions from a fake firm, is a question you might well ask. As Conservative MP Douglas Carswell tweeted , "Can anyone tell me if it was concerns about trade union activity that prompted demands to deal with lobbying? Did I miss something?" But the Tories, who have been outraised by Labour in recent quarters, are determined not to let a good crisis to waste. Having lost the boundary changes, Osborne, who remains the Tories' chief electoral strategist, has seized a new opportunity to tilt the odds in his party's favour.
Labour has responded by rightly describing the move as "a shabby and panicked response by Cameron to divert attention from a set of damaging headlines hitting the Conservative Party", while also emphasising that party funding reform (which all parties accept the need for) should be pursued on a cross-party basis.
But if it is to counter the Tories' dark arts, it must also launch a principled defence of union funding as one of the most open and honest sources of money in politics. Many frequently attempt to draw an equivalence between the unions and the City tycoons and private equity barons who fund the Conservatives , but there is no comparison to be had between the big money donors seeking to buy influence over the Tories and funding from the unions, composed of hundreds of thousands of individual members who have democratically agreed to contribute through the political levy.
Some Tories, most notably Robert Halfon, the MP for Harlow, have rightly urged their party to abandon its kneejerk hostility to the unions. As he wrote in a blog  for The Staggers last year, unions are "essential components of the Big Society. They are the largest voluntary groups in the UK. They are rooted in local communities, and are very much social entrepreneurs. TUC research shows that trade union officers are eight times more likely to engage in voluntary work than the average."
With union membership now on the rise for the first time since 2003, Labour's association with them should be seen as a virtue, not a vice. But unless the party is able to state as much with conviction, the Tories will continue to blacken their name.