I shall vote against a rise in tuition fees because I made a pledge that I would do so. Fees are the poll tax of our generation and I cannot in good conscience vote for an increase. It is not for me to tell colleagues how to vote, but I believe we need to move away from burdening young people with debt. Education should be available to all – not just those who can stomach the debt.

The Liberal Democrat manifesto set out a six-year plan to phase out tuition fees altogether. But let's remember we didn't win the general election, which means our manifesto became a negotiating document. We did an outstanding job of negotiating the coalition: if you comb the coalition agreement you will see that 65% of our manifesto is in it.

The anger of the students is understandable, and I sympathise with it. Seeing thousands of young people engaging with politics is fantastic. My clear message to them is this: the Liberal Democrats are the party of free education – stick with us.

I want to see scrapping fees in our next manifesto. It's great to see that the Scottish Liberal Democrats – who abolished fees when they were in power between 1999 and 2007 – have committed themselves again to keeping Scotland fee-free if they form part of the next Scottish government.

Watching the demonstration on Wednesday made me immensely nostalgic. As a former students' union president and NUS executive member, I've been on plenty of marches. We protested against loans and fees in 1990 when the president of the NUS was Stephen Twigg who, as an education minister, went on to support the introduction of tuition fees – so forgive me for being mildly intolerant of Labour MPs complaining about broken promises. The party that brought in fees, tripled them, refused to give equal rights to poorer part-time students and who commissioned the Browne review do not deserve to be let off the hook.

While Liberal Democrats must accept criticism, it is also about time that this newspaper and others gave us some credit on the student finance package. A Labour or Conservative government would have raised the cap to at least £9,000, but with no progressive mitigation, and part-time students would have received no additional support. The Lib Dems have ensured the abolition of up-front fees for part-time students – this is a massive deal given that roughly half of all students are part-time and most of them are mature, many have family responsibilities and many are poorer than their full-time equivalents.

The raising of the payment threshold from £15,000 to £21,000 is also a significant step. Along with a package of other measures, it means that the poorest 30% of graduates will be better off under the new system. Anyone who wants their analysis of the student finance package to be taken seriously has to acknowledge these advances – and that the progressive parts of the package only happened because of the Lib Dems.

And I'm not going to take lessons on progressive politics from Labour. They spent 13 years in power behaving like Tories, and now six months in opposition behaving like Trots. Accept some responsibility for this mess and, then we might take you seriously.

In the darkest days for the Liberal party, Jo Grimond told our assembly that he would lead us towards the sound of gunfire. Well, after four generations out of power, we're now in the midst of that gunfire – and that means that we are, politically and personally, going to get wounded from time to time.

It feels like that, just at the moment. Being in coalition means daily doses of negotiation and compromise – grownup, pluralistic politics. One day you're up, you win on Trident, the next you lose on fees and you're down again – and then you become the first government to stand up to Rupert Murdoch, and you remember you're doing the right thing.

We could do what Labour have done, lob in a few grenades and then walk away and pretend we had nothing to do with it, or we can aim to make a difference. I choose to make a difference.