TODAY the Scottish Parliament debates Trident.

Over the years there have been many debates on the issue, and in 2007 I was proud to win support for a motion which established for the first time a parliamentary majority against renewing the UK's stock of nuclear weapons.

There are some MSPs who throw up their hands in horror every time we debate a UK-wide issue.

The Labour Party last week objected to giving any parliamentary time at all to debate Trident, or the 10th anniversary of the illegal invasion of Iraq.

But while the decisions on those issues are (regrettably) still taken at Westminster I would be ashamed to be part of a Scottish Parliament which refused to debate them.

Trident deserves to be debated in Scotland. Not only because Scottish public services are suffering so badly while the UK prepares to throw tens of billions of pounds at a new generation of weapons of mass destruction.

Not only because these weapons are based here, making our decisions about the future of Scotland crucial to the UK's plans.

But also because most people in Scotland so consistently oppose Trident.

It's important that Scotland's voice is heard.

Yet this week, when it comes to the vote, I won't be there.

You see, the debate and the vote are taking place at the same time as today's strike action by the PCS union, who represent a quarter of a million public sector staff working to deliver the services we all depend on every day.

They are facing an apparently never-ending series of pay cuts from both UK and Scottish Governments, as well as a raid on their pensions.

They have been opposing George Osborne's socially destructive and economically failed austerity agenda from day one.

And they have chosen today, the day of his latest Budget, to begin a programme of industrial action across the country.

I feel passionately about the Trident debate. But to take part, MSPs must cross the picket lines and walk past the people who provide public services in our constituencies, and who implement the decisions of the Parliament.

I won't be doing that.

Opposing Trident and opposing the UK Government's economic policy are both hugely important to me.

Indeed they are connected, as we see the waste of vast amounts of taxpayers' money on nuclear weapons.

But I don't think it's possible to be on the right side of the argument and the wrong side of the picket line.

Politics is about more than what happens inside a debating chamber, so I'll be working in my local office today instead, and visiting some of the union picket lines to offer my support.