I'm voting against Theresa May's hard Brexit in the House of Lords this week – go ahead and call me an enemy of the people

I am an enemy of the people. Or so the Daily Mail would probably have you believe. For I am a peer and this week I will be voting against Theresa May’s hard Brexit in the hope of inflicting the government’s first Brexit defeat in parliament – and, far more importantly, voting for the right of EU nationals to remain in the UK.

The greatest charge usually levelled against peers is an alleged tendency to look a little somnolent on the red benches. But tomorrow, what goes on in the House of Lords matters more than any day I can remember. We have a huge opportunity to save countless families from being ripped apart, by forcing the Government to do the decent thing and guarantee the right of all EU citizens to remain in the country where they have built their lives, and in the process built up the UK economy.

It’s easy to rubbish the Lords whenever the Government wants to roll over us. But we’re an essential element in our parliamentary democracy. The Lords is a revising chamber. We do not block government legislation, but we can ask them to justify proposals that ministers put forward – and frequently do.

The Commons is far more partisan, dominated by the clash between government ministers and their opposition shadows. Proposals get through there on ambition, loyalty and whipping.

The Lords focuses more deliberately on whether proposals make sense, on the evidence behind them and the details on how they might work. Bills are much more often amended in the Lords than in the Commons, as ministers yield to careful arguments that make them adjust their plans.

So far, the Government’s plans on how to leave the EU are horribly unclear. The White Paper the Prime Minister reluctantly published ducks many of the difficult questions. Special arrangements for specific industries will be fiendishly difficult to negotiate or administer. Open borders for trade are incompatible with leaving the customs union and the European regulatory framework. Insistence on complete sovereignty from rulings of the European Court of Justice will block continued participation in the extensive network of police cooperation, data sharing and intelligence that has grown up since the end of the Cold War, which relies upon agreed checks on misuse of authority to retain mutual confidence.

Brexiteers insist that the people made their decision on June 23^rd, and that Parliament has only a minor role to play on how the government interprets that decision. But the devil is always in the detail, and the referendum campaign left the details of leaving the EU undefined.

The whole idea of parliamentary democracy is that the government is held to account day by day and week by week, not just by occasional referendums. Whether to stay within the single market, how to maintain security cooperation with our neighbours, how to prevent long queues of people and goods at Britain’s frontiers once we leave the EU, are all vital issues from Britain’s future on which Theresa May and her Government have so far provided incoherent answers.

Labour’s abdication of responsible opposition in the Commons makes the role of the Lords even more important. Of course it’s difficult to defend this unelected Chamber – and it suits an embattled government to threaten abolition whenever it is in a corner.

But the advantage of the Lords, even in its current unsatisfactory state, is that its appointed members understand their role as limited but legitimate: to challenge the government when the Commons fails to do its job, to ask awkward questions and to demand reasoned answers.

How the UK leaves the EU is the most important political issue facing the UK. Get it wrong, and the country will be poorer and less secure. In the eight months since the referendum, Brexiteers have repeatedly attacked their critics for their doubts without explaining what future relationship with the countries across the English Channel they want to negotiate.

Of the key ministers, only David Davis seems to have grasped the complexities of Brexit. Liam Fox has travelled to distant lands without making much impact, while Boris Johnson has puzzled and irritated his opposite numbers by the obscurity of his language.

So the Lords, on behalf of the people, the national interest, British industry and British consumers, have the right to ask the Government to think again. My colleagues and I will be voting, this Wednesday, to demand clearer answers – and we will continue to ask for answers as the process of negotiating exit edges uncertainly forward.

William Wallace is a Liberal Democrat peer