Devil's Kitchen claims that contributions from trade unions to the Labour party can be seen as just as corrupt as rich individuals laundering their money through other people to make anonymous large donations to their political party of choice.
This is clearly not the case. In fact a union does the opposite: it groups together lots of small donations into one large donation. A corrupt individual splits a large donation into many small donations, which are then funnelled through proxy donors.
That aside, there is a scandal when it comes to union funding of Labour: the Union Modernisation Fund. By this method. the regime recycles taxpayers' money, via the unions, into Labour donations. Here is a simple diagram created by Guido Fawkes, which explains how it all works:
More info here.
In my opinion, trade unions should stop taking the Government's dirty money and they should stop donating to political parties who ultimately will do nothing for working men and women. Instead they should concentrate on building the new society within the shell of the old.