This evening sees the culmination of five months’ work, led by the Lib Dems, which will finally knock some fairness into the Government’s proposals for reforming the relationship between Labour and the Trade Unions.

Late last year, the Left was raging – with some justification – about a Tory plot to remove up to £6m a year of funding from Labour, by restricting the right of trade unions to collect donations through a political fund.  While the principle of requiring individual ‘opt-in’ consent for such donations is an important one – with which Lib Dems agree – the Government’s endeavour was a naked, one-sided attempt to hobble the opposition.  Real party funding reform cannot be for only one party.  It must also restrict millionaire and big business donations too.

The question our team had to ask was how to amend these elements of the Trade Union Bill without it sounding like simple special pleading for anti-Conservative forces.  Clearly, our party is in a good position to start with, since the Lib Dems do not benefit from trade union political funds.  But we still needed to demonstrate in as non-partisan, dispassionate a way as possible that the what the Government proposed was simply lop-sided and self-interested.

So on the day before the House broke up for Christmas our small Lib Dem Bill team discussed a little-used mechanism to corral principled opposition to the party funding clauses of the Bill.  I suggested that we try to shift this issue to a special Select Committee of the Lords, where Ministers, the Unions, democracy academics, and all the parties could make their case.

This mechanism hadn’t been used since 2005 when Tony Blair first set out to abolish the Lord Chancellor: a big harrumph among their Lordships provoked a Select Committee on that Bill and a delay of some six months.  Having scoured the record for the appropriate procedure, I duly tabled the appropriate ‘amendment to the committal motion’ on the Trade Union Bill.

But there was a snag.  One the Lords’ most infuriating idiosyncrasies is that votes are won and lost according to the time at which they take place.  My amendment would be taken late in the evening on the first day back after Christmas, when many of those we would need to support us wouldn’t be ready and waiting to vote.

Seeing an opportunity, Labour agreed that they would use their clout over the allocation of time in the Lords, to bring the motion I had drafted back to the House at “prime-time”.  What followed was remarkable to witness:  the House backed our motion by 93, against the Government’s will.  Parliamentary officialdom then whirred into action at great speed.  Within just a few days, the special committee was nominated and convened, and a call for evidence was issued.

In less than a month, we produced a comprehensive, cross-party report which – on the basis of all the evidence submitted – concluded unanimously that the Government really could not undertake such a one sided reform in this way.  Cross-party amendments to the Bill were then tabled by the independent, Crossbench Chair of the Committee, Lord Burns, and the Government were defeated on their party funding plans by a whopping 148 majority.

We waited, and waited, to hear how the Government would react.  Then last week, on the day the Lords’ amendments were due to be considered by MPs, Ministers caved in.  The Committee’s demolition job had been so comprehensive, the Government didn’t dare resist.

They accepted the Committee’s conclusions that new trade union members should have to opt-in to any political fund, thereby giving individual consent to political donations.  We want to see this principle extended to all members of trade unions – and that was the Government’s manifesto pledge – but because of the potential loss of £6m a year in income to Labour, it can only come when the Government fulfils – finally – its other, crucial pledge in this area, to “seek agreement on a comprehensive package of party funding reform”.

My cross-party group produced a Draft Bill in 2013, which would do just that.  The Government could do worse than to copy it off our website, and introduce it during this Parliament.

* Lord Tyler is the Liberal Democrat Lords Spokesperson for Political and Constitutional Reform.